Glass articles exhibiting improved fracture performance

ABSTRACT

Embodiments of this disclosure pertain to a strengthened glass article including a first surface and a second surface opposing the first surface defining a thickness (t) of about less than about 1.1 mm, a compressive stress layer extending from the first surface to a depth of compression (DOC) of about 0.1·t or greater, such that when the glass article fracture, it breaks into a plurality of fragments having an aspect ratio of about 5 or less. In some embodiments, the glass article exhibits an equibiaxial flexural strength of about 20 kgf or greater, after being abraded with 90-grit SiC particles at a pressure of 25 psi for 5 seconds. Devices incorporating the glass articles described herein and methods for making the same are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims the benefit of priorityunder 35 U.S.C. § 120 of U.S. application Ser. No. 16/804,271 filed onFeb. 28, 2020, which in turn, is a divisional of and claims the benefitof priority of U.S. application Ser. No. 15/214,602 filed on Jul. 20,2016, now patent Ser. No. 10/579,106 granted Mar. 3, 2020, which inturn, claims the benefit of priority under 35 U.S.C. § 119 of U.S.Provisional Application Ser. No. 62/343,320 filed on May 31, 2016 andU.S. Provisional Application Ser. No. 62/194,984 filed on Jul. 21, 2015,the contents of each of which are relied upon and incorporated herein byreference in their entireties.

BACKGROUND

The disclosure relates to glass articles exhibiting improved fractureperformance, and more particularly to glass articles exhibiting improvedfracture patterns and dicing behavior.

Consumer electronics devices, including handheld devices such as smartphones, tablets, electronic-book readers and laptops often incorporatechemically strengthened glass articles for use as cover glass. As coverglass is directly bonded to a substrate like a touch-panel, display orother structures, when strengthened glass articles fracture, sucharticles may eject small fragments or particles from the free surfacedue to the stored energy created by a combination of surface compressivestresses and tensile stresses beneath the surfaces of the glass. As usedherein, the term fracture includes cracking and/or the formation ofcracks. These small fragments are a potential concern to the deviceuser, especially when fracture occurs in a delayed manner close to theusers face (i.e. eyes and ears), and when the user continues to use andtouch the fractured surface and is, thus, susceptible to minor cuts orabrasions, especially when crack distances are relatively long andfragments with sharp corners and edges are present.

Accordingly, there is a need for glass articles that exhibit a modifiedfragmentation behavior so that when such articles fracture, they exhibitan enhanced dicing behavior, such as, for example, a dicing effectgenerating short crack lengths and fewer ejected particles. Moreover,there is also a need for glass articles that, when fractured, ejectfewer fragments and fragments with less kinetic energy and momentum.

SUMMARY

A first aspect of this disclosure pertains to a strengthened glassarticle including a first surface and a second surface opposing thefirst surface defining a thickness (t) of about 1.1 mm or less, and acompressive stress layer extending from the first surface to a depth ofcompression (DOC) of greater than about 0.11·t. In some embodiments,after the glass article fractures, the glass article includes aplurality of fragments, wherein at least 90% of the plurality offragments have an aspect ratio of about 5 or less, the glass articlefractures into the plurality of fragments in 1 second or less, asmeasured by a Frangibility Test.

In some embodiments, the strengthened glass article exhibiting anequibiaxial flexural strength of about 20 kgf or greater, after beingabraded with 90-grit SiC particles at a pressure of 25 psi for 5seconds. In some embodiments, the strengthened glass article may, afterthe glass article fractures, comprises fractures such that 50% or moreof the fractures extend only partially through the thickness.

A third aspect of this disclosure pertains to a device including astrengthened glass substrate, as described herein, a containment layer;and a support, wherein the device comprises a tablet, a transparentdisplay, a mobile phone, a video player, an information terminal device,an e-reader, a laptop computer, or a non-transparent display.

A fourth aspect of this disclosure pertains to a consumer electronicsproduct including a housing having a front surface, electricalcomponents provided at least partially internal to the housing, theelectrical components including at least a controller, a memory, and adisplay; and a cover glass disposed at the front surface of the housingand over the display, the cover glass comprising a strengthened glassarticle as described herein.

Additional features and advantages will be set forth in the detaileddescription which follows, and in part will be readily apparent to thoseskilled in the art from that description or recognized by practicing theembodiments as described herein, including the detailed descriptionwhich follows, the claims, as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description are merely exemplary, and areintended to provide an overview or framework to understanding the natureand character of the claims. The accompanying drawings are included toprovide a further understanding, and are incorporated in and constitutea part of this specification. The drawings illustrate one or moreembodiment(s), and together with the description serve to explainprinciples and operation of the various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a side view of a glass article according to one or moreembodiments;

FIG. 1B is a side view of the glass article of FIG. 1A after fracture;

FIG. 2 is a cross-sectional view across a thickness of a known thermallytempered glass-based article;

FIG. 3 is a cross-sectional view across a thickness of a knownchemically strengthened glass-based article;

FIG. 4 is a cross-sectional view across a thickness of a strengthenedglass-based article according to one or more embodiments;

FIG. 5 is a is a schematic cross-sectional view of a ring-on-ringapparatus;

FIG. 6 is a schematic cross-sectional view of an embodiment of theapparatus that is used to perform the inverted ball on sandpaper (IBoS)test described in the present disclosure;

FIG. 7 is a schematic cross-sectional representation of the dominantmechanism for failure due to damage introduction plus bending thattypically occurs in glass-based articles that are used in mobile or handheld electronic devices;

FIG. 8 is a flow chart for a method of conducting the IBoS test in theapparatus described herein; and

FIG. 9A is a side view of the glass article of FIG. 1A including acontainment layer;

FIG. 9B is a side view the glass article of FIG. 9A including a secondcontainment layer;

FIG. 10 is a front plan view of an electronic device incorporating oneor more embodiments of the glass articles described herein.

FIG. 11 is a graph showing AROR test results for Example 1;

FIG. 12 is a graph showing drop test results for Example 2;

FIG. 13 is a plot showing the concentration of K₂O as a function of ionexchange depth for Example 4;

FIG. 14 is a plot showing the stress profile of Example 4G;

FIGS. 15A-15D are fracture images of Example 5;

FIGS. 16A-16D are images showing the readability of Example 6 afterfracture at different viewing angles;

FIG. 17 is a plot of calculated stored tensile energy as a function ofion-exchange time, for Example 7; and

FIG. 18 is a plot of calculated central tension as a function ofion-exchange time, for Example 7; and

FIG. 19 is a plot showing the stress profile of Example 6, withcompressive and tensile stress plotted as function of depth.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments, examples ofwhich are illustrated in the accompanying drawings. Referring to thedrawings in general, it will be understood that the illustrations arefor the purpose of describing particular embodiments and are notintended to limit the disclosure or appended claims thereto. Thedrawings are not necessarily to scale, and certain features and certainviews of the drawings may be shown exaggerated in scale or in schematicin the interest of clarity and conciseness.

In the following description, like reference characters designate likeor corresponding parts throughout the several views shown in thefigures. It is also understood that, unless otherwise specified, termssuch as “top,” “bottom,” “outward,” “inward,” and the like are words ofconvenience and are not to be construed as limiting terms. In addition,whenever a group is described as comprising at least one of a group ofelements and combinations thereof, it is understood that the group maycomprise, consist essentially of, or consist of any number of thoseelements recited, either individually or in combination with each other.Similarly, whenever a group is described as consisting of at least oneof a group of elements or combinations thereof, it is understood thatthe group may consist of any number of those elements recited, eitherindividually or in combination with each other. Unless otherwisespecified, a range of values, when recited, includes both the upper andlower limits of the range as well as any ranges therebetween. As usedherein, the indefinite articles “a,” “an,” and the correspondingdefinite article “the” mean “at least one” or “one or more,” unlessotherwise specified. It also is understood that the various featuresdisclosed in the specification and the drawings can be used in any andall combinations.

It is noted that the terms “substantially” and “about” may be utilizedherein to represent the inherent degree of uncertainty that may beattributed to any quantitative comparison, value, measurement, or otherrepresentation. These terms are also utilized herein to represent thedegree by which a quantitative representation may vary from a statedreference without resulting in a change in the basic function of thesubject matter at issue.

As used herein, the term “glass article” is used in its broadest senseto include any object made wholly or partly of glass. Glass articlesinclude laminates of glass and non-glass materials, laminates ofamorphous and crystalline materials, and glass-ceramics (including anamorphous phase and a crystalline phase). Unless otherwise specified,all compositions are expressed in terms of mole percent (mol %).

As will be discussed herein, embodiments of the glass articles mayinclude strengthened glass or glass ceramic materials that exhibitimproved mechanical performance and reliability compared to known glassarticles, especially known cover glass articles. Embodiments of theglass articles described herein may exhibit fragmentation behaviors thatare not exhibited by known cover glass articles. In this disclosureglass-based substrates are generally unstrengthened and glass-basedarticles generally refer to glass-based substrates that have beenstrengthened (by, for example, ion exchange).

A first aspect of this disclosure pertains to a strengthened glassarticle that exhibits the ability to fracture into a dense fracturepattern with a dicing effect that is analogous to fully, thermallytempered glass used in shower panels or automobile window panels. Insome embodiments, the fragments are intended to be less injurious tohumans. Such articles exhibit this behavior despite being chemicallystrengthened and having thicknesses significantly less than achievableby current known thermal tempering processes. In some embodiments, thefragments are even smaller or finer than those observed with knownthermally tempered glass. For example, embodiments of the glass articlesexhibit a “dicing” effect in that, when the glass article is fractured,the “diced” fragments have a small aspect ratio and the fracturegenerated surface and the as-formed surface form larger angles (i.e.,fewer blade-like or knife-like angles), such that the fragments resemblecubes more than splinters, as described in more detail below withrespect to FIG. 1A. In some instances, the diced fragments are limitedby a maximum or longest dimension of 2 millimeters (mm) or less in anydirection of the major plane of the glass article. In some instances,when fractured or after the glass article fractures, the glass articleincludes a plurality of fragments having an average aspect ratio ofabout 10 or less, or about 5 or less (e.g., about 4.5 or less, about 4or less, about 3.5 or less, about 3 or less, about 2.5 or less, about 2or less). In some embodiments, the average aspect ratio of the pluralityof fragments is in the range from about 1 to about 2. In some instances,about 90% or greater, or about 80% or greater of the plurality offragments exhibits the average aspect ratios described herein. As usedherein, the term “aspect ratio” refers to the ratio of the longest ormaximum dimension of a fragment to the shortest or minimum dimension ofthe fragment. The term “dimension” can include a length, width,diagonal, or thickness. Glass articles that exhibit such fragments afterbeing fractured may be characterized herein as exhibiting “dicing”behavior.

Referring to FIGS. 1A and 1 i, in one or more embodiments, the glassarticles 10 described herein may have a sheet configuration withopposing major surfaces 12, 14 and opposing minor surfaces 16, 18. Atleast one major surface 12 forms an “as-formed” surface of the glassarticle. When fractured, a new surface generated by the fracture of theglass article, is formed (i.e., a “fracture-generated” surface),indicated by reference number 19 in FIG. 1B. The angle α between afracture generated surface and the as-formed surface (after the glassarticle is fractured) are in the range from about 85 degrees to about 95degrees or about 88 degrees to about 92 degrees. In one or moreembodiments, about 90% or more of the plurality of fragments in glassarticle exhibit the angles between the as-formed surface and all of thefracture generated surfaces, after the glass article is fractured.

In one or more embodiments, at least 50% (e.g., about 60% or more, about70% or more, about 80% or more, or about 90% or more) of the pluralityof fragments have a maximum dimension that is less than or equal to 5·t,less than or equal to 3·t, or less than or equal to 3·t. In someinstances, at least 50% (e.g., about 60% or more, about 70% or more,about 80% or more, or about 90% or more) of plurality of fragmentscomprise a maximum dimension that is less than 2 times the minimumdimension. In some embodiments, the maximum dimension is about 1.8 timesthe minimum dimension or less, about 1.6 times the minimum dimension orless, about 1.5 times the minimum dimension or less, about 1.4 times theminimum dimension or less, about 1.2 times the minimum dimension orless, or about equal to the minimum dimension.

In one or more embodiments, at least 50% (e.g., about 60% or more, about70% or more, about 80% or more, or about 90% or more) of the pluralityof fragments comprises a volume of less than or equal to about 10 mm³.In some embodiments, the volume may be less than or equal to about 8mm³, less than or equal to about 5 mm³, or less than or equal to about 4mm³. In some embodiments, the volume may be in the range from about 0.1mm³ to about 1.5 mm³.

As used herein, the phrase “strengthened articles” includes articlesthat are chemically strengthened, or chemically strengthened andthermally strengthened, but exclude articles that are only thermallystrengthened. As shown in FIG. 4 , the strengthened glass articleexhibits a stress profile that can be characterized in terms of asurface compressive stress (CS), a central tension (CT) and a depth ofcompression (DOC).

The stress profile exhibited by the strengthened glass articles of oneor more embodiments may be distinguished between the stress profilesexhibited by known thermally tempered glass articles and knownchemically strengthened glass articles. Traditionally, thermallytempered glass has been used to prevent failures where such flaws may beintroduced to the glass because thermally tempered glass often exhibitslarge CS layers (e.g., approximately 21% of the total thickness of theglass), which can prevent flaws from propagating and thus, failure. Anexample of a stress profile generated by thermal tempering is shown inFIG. 2 . In FIG. 2 , the thermally treated glass article 100 includes afirst surface 101, a thickness t₁, and a surface CS 110. The glassarticle 100 exhibits a CS that decreases from the first surface 101 to aDOC 130, as defined herein, at which depth the stress changes fromcompressive to tensile stress and reaches a CT 120.

Thermal tempering is currently limited to thick glass articles (i.e.,glass articles having a thickness t₁ of about 3 millimeters or greater)because, to achieve the thermal strengthening and the desired residualstresses, a sufficient thermal gradient must be formed between the coreof such articles and the surface. Such thick articles are undesirable ornot practical in many applications such as displays (e.g., consumerelectronics, including mobile phones, tablets, computers, navigationsystems, and the like), architecture (e.g., windows, shower panels,countertops etc.), transportation (e.g., automotive, trains, aircraft,sea craft, etc.), appliances, packaging, or any application thatrequires superior fracture resistance but thin and light-weightarticles.

Known chemically strengthened glass articles do not exhibit the stressprofile of thermally tempered glass articles, although chemicalstrengthening is not limited by the thickness of the glass article inthe same manner as thermally tempering. An example of a stress profilegenerated by chemical strengthening (e.g., by ion exchange process), isshown in FIG. 3 . In FIG. 3 , the chemically strengthened glass article200 includes a first surface 201, a thickness t₂ and a surface CS 210.The glass article 200 exhibits a CS that decreases from the firstsurface 201 to a DOC 230, as defined herein, at which depth the stresschanges from compressive to tensile stress and reaches a CT 220. Asshown in FIG. 3 , such profiles exhibit a flat CT region or CT regionwith a constant or near constant tensile stress and, often, a lower CTvalue, as compared to the CT value shown in FIG. 2 .

The glass articles of one or more embodiments of this disclosure exhibita thickness t of less than about 3 mm (e.g., about 2 mm or less, about1.5 mm or less, or about 1.1 mm or less) and a compressive stress layerextending from the first surface to a DOC of about 0.1·t or greater. Asused herein, DOC refers to the depth at which the stress within theglass article changes compressive to tensile stress. At the DOC, thestress crosses from a positive (compressive) stress to a negative(tensile) stress (e.g., 130 in FIG. 2 ) and thus exhibits a stress valueof zero.

According to the convention normally used in the art, compression isexpressed as a negative (<0) stress and tension is expressed as apositive (>0) stress. Throughout this description, however, CS isexpressed as a positive or absolute value—i.e., as recited herein,CS=|CS|.

In particular, the glass articles described herein are thin and exhibitstress profiles that are typically only achievable through temperingthick glass articles (e.g., having a thickness of about 2 mm or 3 mm orgreater). In some cases, the glass articles exhibit a greater surface CSthan tempered glass articles. In one or more embodiments, the glassarticles exhibit a larger depth of the compression layer (in which theCS decreases and increases more gradually than known chemicallystrengthened glass articles) such that the glass article exhibitssubstantially improved fracture resistance, even when the glass articleor a device including the same is dropped on a hard, rough surface. Theglass articles of one or more embodiments exhibit a greater CT valuethan some known chemically strengthened glass substrates.

CS is measured by surface stress meter (FSM) using commerciallyavailable instruments such as the FSM-6000, manufactured by OriharaIndustrial Co., Ltd. (Japan). Surface stress measurements rely upon theaccurate measurement of the stress optical coefficient (SOC), which isrelated to the birefringence of the glass. SOC in turn is measuredaccording to a modified version of Procedure C described in ASTMstandard C770-98 (2013), entitled “Standard Test Method for Measurementof Glass Stress-Optical Coefficient,” the contents of which areincorporated herein by reference in their entirety. The modificationincludes using a glass disc as the specimen with a thickness of 5 to 10mm and a diameter of 12.7 mm, wherein the disc is isotropic andhomogeneous and core drilled with both faces polished and parallel. Themodification also includes calculating the maximum force, Fmax to beapplied. The force should be sufficient to produce at least 20 MPacompression stress. Fmax is calculated as follows:

-   -   Fmax=7.854*D*h    -   Where:    -   Fmax=Force in Newtons    -   D=the diameter of the disc    -   h=the thickness of the light path        For each force applied, the stress is computed as follows:    -   σ_(MPa)=8F/(π*D*h)    -   Where:    -   F=Force in Newtons    -   D=the diameter of the disc    -   h=the thickness of the light path

CT values are measured using a scattered light polariscope (“SCALP”,supplied by Glasstress Ltd., located in Tallinn, Estonia, under modelnumber SCALP-04) and techniques known in the art. SCALP can also be usedto measure the DOC, as will be described in more detail below.

In some embodiments, the glass article may also exhibit a depth ofpenetration of potassium ions (“Potassium DOL”) that is distinct fromthe DOC. The degree of difference between DOC and Potassium DOL dependson the glass substrate composition and the ion exchange treatment thatgenerates the stress in the resulting glass article. Where the stress inthe glass article is generated by exchanging potassium ions into theglass article, FSM (as described above with respect to CS) is used tomeasure Potassium DOL. Where the stress is generated by exchangingsodium ions into the glass article, SCALP (as described above withrespect to CT) is used to measure DOC and the resulting glass articlewill not have a Potassium DOL since there is no penetration of potassiumions. Where the stress in the glass article is generated by exchangingboth potassium and sodium ions into the glass, the exchange depth ofsodium indicates the DOC, and the exchange depth of potassium ionsindicates a change in the magnitude of the compressive stress (but notthe change in stress from compressive to tensile); in such embodiments,the DOC is measured by SCALP, and Potassium DOL is measured by FSM.Where both Potassium DOL and DOC are present in a glass article, thePotassium DOL is typically less than the DOC.

Refracted near-field (RNF) method or SCALP may be used to measure thestress profile in the glass articles described herein (regardless ofwhether the stress is generated by sodium ion exchange and/or potassiumion exchange). When the RNF method is utilized, the CT value provided bySCALP is utilized. In particular, the stress profile measured by RNF isforce balanced and calibrated to the CT value provided by a SCALPmeasurement. The RNF method is described in U.S. Pat. No. 8,854,623,entitled “Systems and methods for measuring a profile characteristic ofa glass sample”, which is incorporated herein by reference in itsentirety. In particular, the RNF method includes placing the glass-basedarticle adjacent to a reference block, generating apolarization-switched light beam that is switched between orthogonalpolarizations at a rate of between 1 Hz and 50 Hz, measuring an amountof power in the polarization-switched light beam and generating apolarization-switched reference signal, wherein the measured amounts ofpower in each of the orthogonal polarizations are within 50% of eachother. The method further includes transmitting thepolarization-switched light beam through the glass sample and referenceblock for different depths into the glass sample, then relaying thetransmitted polarization-switched light beam to a signal photodetectorusing a relay optical system, with the signal photodetector generating apolarization-switched detector signal. The method also includes dividingthe detector signal by the reference signal to form a normalizeddetector signal and determining the profile characteristic of the glasssample from the normalized detector signal.

In one or more embodiments in which the stress in a glass article isgenerated by only potassium ion exchange and Potassium DOL is equivalentto DOC, the stress profile may also be obtained by the methods disclosedin U.S. patent application Ser. No. 13/463,322, entitled “Systems AndMethods for Measuring the Stress Profile of Ion-Exchanged Glass(hereinafter referred to as “Roussev I”),” filed by Rostislav V. Roussevet al. on May 3, 2012, and claiming priority to U.S. Provisional PatentApplication No. 61/489,800, having the same title and filed on May 25,2011. Roussev I discloses methods for extracting detailed and precisestress profiles (stress as a function of depth) of chemicallystrengthened glass using FSM. Specifically, the spectra of bound opticalmodes for TM and TE polarization are collected via prism couplingtechniques, and used in their entirety to obtain detailed and precise TMand TE refractive index profiles n_(TM)(z) and n_(TE)(z). The contentsof the above applications are incorporated herein by reference in theirentirety. The detailed index profiles are obtained from the mode spectraby using the inverse Wentzel-Kramers-Brillouin (IWKB) method, andfitting the measured mode spectra to numerically calculated spectra ofpre-defined functional forms that describe the shapes of the indexprofiles and obtaining the parameters of the functional forms from thebest fit. The detailed stress profile S(z) is calculated from thedifference of the recovered TM and TE index profiles by using a knownvalue of the stress-optic coefficient (SOC):

S(z)=[n _(TM)(z)−n _(TE)(z)]/SOC  (2).

Due to the small value of the SOC, the birefringence n_(TM)(z)−n_(TE)(z)at any depth z is a small fraction (typically on the order of 1%) ofeither of the indices n_(TM)(z) and n_(TE)(z). Obtaining stress profilesthat are not significantly distorted due to noise in the measured modespectra requires determination of the mode effective indices withprecision on the order of 0.00001 RIU. The methods disclosed in RoussevI further include techniques applied to the raw data to ensure such highprecision for the measured mode indices, despite noise and/or poorcontrast in the collected TE and TM mode spectra or images of the modespectra. Such techniques include noise-averaging, filtering, and curvefitting to find the positions of the extremes corresponding to the modeswith sub-pixel resolution.

As stated above, the glass articles described herein may be chemicallystrengthened by ion exchange and exhibit stress profiles that aredistinguished from those exhibited by known strengthened glass. In thisprocess, ions at or near the surface of the glass article are replacedby—or exchanged with—larger ions having the same valence or oxidationstate. In those embodiments in which the glass article comprises analkali aluminosilicate glass, ions in the surface layer of the glass andthe larger ions are monovalent alkali metal cations, such as Li⁺ (whenpresent in the glass article), Na⁺, K⁺, Rb⁺, and Cs⁺. Alternatively,monovalent cations in the surface layer may be replaced with monovalentcations other than alkali metal cations, such as Ag⁺ or the like.

Ion exchange processes are typically carried out by immersing a glassarticle in a molten salt bath (or two or more molten salt baths)containing the larger ions to be exchanged with the smaller ions in theglass article. It should be noted that aqueous salt baths may also beutilized. In addition, the composition of the bath(s) may include morethan one type of larger ion (e.g., Na+ and K+) or a single larger ion.It will be appreciated by those skilled in the art that parameters forthe ion exchange process, including, but not limited to, bathcomposition and temperature, immersion time, the number of immersions ofthe glass article in a salt bath (or baths), use of multiple salt baths,additional steps such as annealing, washing, and the like, are generallydetermined by the composition of the glass article (including thestructure of the article and any crystalline phases present) and thedesired DOC and CS of the glass article that result from thestrengthening operation. By way of example, ion exchange of a glassarticles may be achieved by immersion of the glass articles in at leastone molten bath containing a salt such as, but not limited to, nitrates,sulfates, and chlorides of the larger alkali metal ion. Typical nitratesinclude KNO₃, NaNO₃, LiNO₃, NaSO₄ and combinations thereof. Thetemperature of the molten salt bath typically is in a range from about380° C. up to about 450° C., while immersion times range from about 15minutes up to about 100 hours depending on glass thickness, bathtemperature and glass diffusivity. However, temperatures and immersiontimes different from those described above may also be used.

In one or more embodiments, the glass articles may be immersed in amolten salt bath of 100% NaNO₃ having a temperature from about 370° C.to about 480° C. In some embodiments, the glass substrate may beimmersed in a molten mixed salt bath including from about 5% to about90% KNO₃ and from about 10% to about 95% NaNO₃. In some embodiments, theglass substrate may be immersed in a molten mixed salt bath includingNa₂SO₄ and NaNO₃ and have a wider temperature range (e.g., up to about500° C.). In one or more embodiments, the glass article may be immersedin a second bath, after immersion in a first bath. Immersion in a secondbath may include immersion in a molten salt bath including 100% KNO₃ for15 minutes to 8 hours.

The ion exchange conditions may be modified based on the glasscomposition and thickness of the glass substrate. For example, a glasssubstrate having a nominal composition as shown in Example 1 belowhaving a thickness of 0.4 mm may be immersed in a molten salt bath of80-100% KNO₃ (with the balance NaNO₃) having a temperature of about 460°C. for a duration from about 10 hours to about 20 hours. The samesubstrate having a thickness of about 0.55 mm may be immersed in amolten salt bath of 70-100% KNO₃ (with the balance NaNO₃) having atemperature of about 460° C. for a duration of from about 20 hours toabout 40 hours. The same substrate having a thickness of about 0.8 mmmay be immersed in a molten salt bath of 60-100% KNO₃ (with the balanceNaNO₃) having a temperature of about 460° C. for a duration of fromabout 40 hours to about 80 hours.

In one or more embodiments, the glass-based substrate may be immersed ina molten, mixed salt bath including NaNO₃ and KNO₃ (e.g., 49%/51%,50%/50%, 51%/49%) having a temperature less than about 420° C. (e.g.,about 400° C. or about 380° C.). for less than about 5 hours, or evenabout 4 hours or less.

Ion exchange conditions can be tailored to provide a “spike” or toincrease the slope of the stress profile at or near the surface of theresulting glass-based article. This spike can be achieved by single bathor multiple baths, with the bath(s) having a single composition or mixedcomposition, due to the unique properties of the glass compositions usedin the glass-based articles described herein.

As illustrated in FIG. 4 , the glass article 300 of one or moreembodiments includes a first surface 302 and a second surface 304opposing the first surface, defining a thickness t. In one or moreembodiments, the thickness t may be less than about 3 mm, about 2 mm orless, about 1.5 mm or less, about 1.1 mm or less, or 1 mm or less (e.g.,in the range from about 0.01 mm to about 1.5 mm, from about 0.1 mm toabout 1.5 mm, from about 0.2 mm to about 1.5 mm, from about 0.3 mm toabout 1.5 mm, from about 0.4 mm to about 1.5 mm, in the range from about0.01 mm to about 1.1 mm, from about 0.1 mm to about 1.1 mm, from about0.2 mm to about 1.1 mm, from about 0.3 mm to about 1.1 mm, from about0.4 mm to about 1.1 mm, from about 0.01 mm to about 1.4 mm, from about0.01 mm to about 1.2 mm, from about 0.01 mm to about 1.1.1 mm, fromabout 0.01 mm to about 1 mm, from about 0.01 mm to about 0.9 mm, fromabout 0.01 mm to about 0.8 mm, from about 0.01 mm to about 0.7 mm, fromabout 0.01 mm to about 0.6 mm, from about 0.01 mm to about 0.5 mm, fromabout 0.1 mm to about 0.5 mm, or from about 0.3 mm to about 0.5 mm.)

FIG. 4 , is a cross-sectional illustration of the stress profile of achemically strengthened glass article 300 along its thickness 330(depicted along the x-axis). The magnitude of the stress is illustratedon the y-axis with the line 301 representing a zero stress.

The stress profile 312 includes a CS layer 315 (with a surface CS value310) that extends from one or both the first major surface 302 and thesecond major surface 304 to a DOC 330, and a CT layer 325 (with a CT320) that extends from DOC 330 to the central portion of the article.

As used herein, DOC refers to the depth at which the stress within theglass article changes compressive to tensile. At the DOC, the stresscrosses from a positive (compressive) stress to a negative (tensile)stress (e.g., 330 in FIG. 5 ) and thus exhibits a stress value of zero.

The CS layer has an associated depth or length 317 extending from amajor surface 302, 304 to the DOC 330. The CT layer 325 also has anassociated depth or length 327 (CT region or layer).

The surface CS 310 may be about 150 MPa or greater or about 200 MPa orgreater (e.g., about 250 MPa or greater, about 300 MPa or greater, about400 MPa or greater, about 450 MPa or greater, about 500 MPa or greater,or about 550 MPa or greater). The surface CS 310 may be up to about 900MPa, up to about 1000 MPa, up to about 1100 MPa, or up to about 1200MPa. In one or more embodiments, the surface CS 310 may be in a rangefrom about 150 MPa to about 1200 MPa, from about 200 MPa to about 1200MPa, from about 250 MPa to about 1200 MPa, from about 300 MPa to about1200 MPa, from about 350 MPa to about 1200 MPa, from about 400 MPa toabout 1200 MPa, from about 450 MPa to about 1200 MPa, from about 500 MPato about 1200 MPa, from about 200 MPa to about 1100 MPa, from about 200MPa to about 1000 MPa, from about 200 MPa to about 900 MPa, from about200 MPa to about 800 MPa, from about 200 MPa to about 700 MPa, fromabout 200 MPa to about 600 MPa, from about 200 MPa to about 500 MPa,from about 300 MPa to about 900 MPa, or from about 400 MPa to 600 MPa.

The CT 320 may be about 25 MPa or greater, about 50 MPa or greater,about 75 MPa or greater, or about 85 MPa or greater, or about 100 MPa orgreater (e.g., about 150 MPa or greater, about 200 MPa or greater, 250MPa or greater, or about 300 MPa or greater). In some embodiments, theCT 320 may be in the range from about 50 MPa to about 400 MPa, (e.g.,from about 75 MPa to about 400 MPa, from about 100 MPa to about 400 MPa,from about 150 MPa to about 400 MPa, from about 50 MPa to about 350 MPa,from about 50 MPa to about 300 MPa, from about 50 MPa to about 250 MPa,from about 50 MPa to about 200 MPa, from about 100 MPa to about 400 MPa,from about 100 MPa to about 300 MPa, from about 150 MPa to about 250MPa). As used herein, CT is the greatest magnitude of the centraltension in the glass article.

It should be noted that any one or more of surface CS 310 and CT 320 maybe dependent on the thickness of the glass article. For example, glassarticles having at thickness of about 0.8 mm may have a CT of about 100MPa or greater. In one or more embodiment, glass articles having atthickness of about 0.4 mm may have a CT of about 130 MPa or greater. Insome embodiments, the CT may be expressed in terms of thickness t of theglass article. For example, in one or more embodiment CT may be about(100 MPa)/√(t/1 mm), or greater, where t is thickness is mm. In someembodiments, CT may be about (105 MPa)/√(t/1 mm) or greater, (110MPa)/√(t/1 mm) or greater, (115 MPa)/√(t/1 mm) or greater, (120MPa)/√(t/1 mm) or greater, or (125 MPa)/√(t/1 mm) or greater.

The CT 320 may be positioned at a range from about 0.3·t to about 0.7·t,from about 0.4·t to about 0.6·t or from about 0.45·t to about 0.55·t. Itshould be noted that any one or more of surface CS 310 and CT 320 may bedependent on the thickness of the glass-based article. For example,glass-based articles having at thickness of about 0.8 mm may have a CTof about 75 MPa or less. When the thickness of the glass-based articledecreases, the CT may increase. In other words, the CT increases withdecreasing thickness (or as the glass-based article becomes thinner).

The Young's modulus of the glass article can influence the CT of thestrengthened glass articles described herein. Specifically, as theYoung's modulus of a glass article decreases, the glass article may bestrengthened to have a lower CT, for a given thickness, and stillexhibit the fracture behavior described herein. For example, whencomparing a 1 mm glass article having a relatively lower Young's modulusthan another 1 mm-thick glass article having a higher Young's modulus,the lower Young's modulus glass article may be strengthened to a lesserdegree (i.e., to a relatively lower CT value) and still exhibit the samefracture behavior as the higher Young's modulus glass (which would havea higher CT compared to the CT glass article).

In some embodiments, the ratio of the CT 320 to the surface CS in therange from about 0.05 to about 1 (e.g., in the range from about 0.05 toabout 0.5, from about 0.05 to about 0.3, from about 0.05 to about 0.2,from about 0.05 to about 0.1, from about 0.5 to about 0.8, from about0.0.5 to about 1, from about 0.2 to about 0.5, from about 0.3 to about0.5). In known chemically strengthened glass articles, the ratio of theCT 320 to the surface CS is 0.1 or less. In some embodiments, surface CSmay be 1.5 times (or 2 times or 2.5 times) the CT or greater. In someembodiments, the surface CS may be up to about 20 times the CT.

In one or more embodiments, the stress profile 312 comprises a maximumCS, which is typically the surface CS 310 and can be found at one orboth of the first surface 302 and the second surface 304. In one or moreembodiments, the CS layer or region 315 extends along a portion of thethickness to the DOC 317 and a CT 320. In one or more embodiments, theDOC 317 may be about 0.1·t or greater. For example, the DOC 317 may beabout 0.12·t or greater, about 0.14·t or greater, about 0.15·t orgreater, about 0.16·t or greater, 0.17·t or greater, 0.18·t or greater,0.19·t or greater, 0.20·t or greater, about 0.21·t or greater, or up toabout 0.25·t. In some embodiments, the DOC 317 is less than the maximumchemical depth 342. The maximum chemical depth 342 may be about 0.4·t orgreater, 0.5·t or greater, about 55·t or greater, or about 0.6·t orgreater.

In one or more embodiments, the glass-based article comprises aPotassium DOL in the range from about 6 micrometers to about 20micrometers. In some embodiments, the Potassium DOL may be expressed asa function of the thickness t of the glass-based article. In one or moreembodiments, Potassium DOL may be in the range from about 0.005t toabout 0.05t. In some embodiments, the Potassium DOL may be in the rangefrom about 0.005t to about 0.05t, from about 0.005t to about 0.045t,from about 0.005t to about 0.04t, from about 0.005t to about 0.035t,from about 0.005t to about 0.03t, from about 0.005t to about 0.025t,from about 0.005t to about 0.02t, from about 0.005t to about 0.015t,from about 0.005t to about 0.01t, from about 0.006t to about 0.05t, fromabout 0.008t to about 0.05t, from about 0.01t to about 0.05t, from about0.015t to about 0.05t, from about 0.02t to about 0.05t, from about0.025t to about 0.05t, from about 0.03t to about 0.05t, or from about0.01t to about 0.02t.

In one or more embodiments, the compressive stress value at thePotassium DOL depth may be in the range from about 50 MPa to about 300MPa. In some embodiments, the compressive stress value at the PotassiumDOL depth may be in the range from about 50 MPa to about 280 MPa, fromabout 50 MPa to about 260 MPa, from about 50 MPa to about 250 MPa, fromabout 50 MPa to about 240 MPa, from about 50 MPa to about 220 MPa, fromabout 50 MPa to about 200 MPa, from about 60 MPa to about 300 MPa, fromabout 70 MPa to about 300 MPa, from about 75 MPa to about 300 MPa, fromabout 80 MPa to about 300 MPa, from about 90 MPa to about 300 MPa, fromabout 100 MPa to about 300 MPa, from about 1100 MPa to about 300 MPa,from about 120 MPa to about 300 MPa, from about 130 MPa to about 300MPa, or from about 150 MPa to about 300 MPa.

In one or more embodiments, the glass article exhibits the combinationof a surface CS in a range from about 450 MPa to about 600 MPa, a CT ina range from about 200 to 300 MPa, and a thickness in a range from about0.4 mm to 0.5 mm. In some embodiments, the DOC of the glass article isin a range from about 0.18t to about 0.21t.

In one or more embodiments, the glass article exhibits the combinationof a surface CS in a range from about 350 MPa to about 450 MPa, a CT ina range from about 150 to 250 MPa, and a thickness in a range from about0.4 mm to 0.5 mm. In some embodiments, the DOC of the glass article isin a range from about 0.18t to about 0.21t.

In one or more embodiments, the glass articles exhibits a maximumchemical depth of about 0.4·t or greater, 0.5·t or greater, about 55·tor greater, or about 0.6·t or greater. As used herein, the term“chemical depth” means the depth at which an ion of the metal oxide oralkali metal oxide (e.g., the metal ion or alkali metal ion) diffusesinto the glass article and the depth at which the concentration of thation reaches a minimum value, as determined by Electron ProbeMicro-Analysis (EPMA). The ion is the ion diffused into the chemicallystrengthened glass article as a result of ion exchange. Maximum chemicaldepth refers to the maximum diffusion depth of any ion exchanged intothe chemically strengthened glass article by ion exchange process. Forexample, where a molten salt bath having more than one diffusing ionicspecies (i.e., a molten salt bath of both NaNO₃ and KNO₃), the differentionic species may diffuse to different depths into the chemicallystrengthened glass articles. The maximum chemical depth is the greatestdiffusion depth of all the ionic species ion exchanged into thechemically strengthened glass article.

In one or more embodiments, the stress profile 312 may be described asparabolic-like in shape. In some embodiments, the stress profile alongthe region or depth of the glass-based article exhibiting tensile stressexhibits a parabolic-like shape. In one or more specific embodiments,the stress profile 312 is free of a flat stress (i.e., compressive ortensile) portion or a portion that exhibits a substantially constantstress (i.e., compressive or tensile). In some embodiments, the CTregion exhibits a stress profile that is substantially free of a flatstress or free of a substantially constant stress. In one or moreembodiments, all points of the stress profile 312 between a thicknessrange from about 0t up to about 0.2·t and greater than 0.8·t (or fromabout 0·t to about 0.3·t and greater than 0.7·t) comprise a tangent thatis less than about −0.1 MPa/micrometers or greater than about 0.1MPa/micrometers. In some embodiments, the tangent may be less than about−0.2 MPa/micrometers or greater than about 0.2 MPa/micrometers. In somemore specific embodiments, the tangent may be less than about −0.3MPa/micrometers or greater than about 0.3 MPa/micrometers. In even morespecific embodiments, the tangent may be less than about −0.5MPa/micrometers or greater than about 0.5 MPa/micrometers. In otherwords, the stress profile of one or more embodiments along thesethickness ranges (i.e., 0·t up to about 2·t and greater than 0.8t, orfrom about 0t to about 0.3·t and 0.7·t or greater) exclude points havinga tangent, as described herein. Without being bound by theory, knownerror function or quasi-linear stress profiles have points along thesethickness ranges (i.e., from about 0·t up to about 2·t and greater than0.8·t, or from about 0·t to about 0.3·t and 0.7·t or greater) that havea tangent that is in the range from about −0.1 MPa/micrometers to about0.1 MPa/micrometers, from about −0.2 MPa/micrometers to about 0.2MPa/micrometers, from about −0.3 MPa/micrometers to about 0.3MPa/micrometers, or from about −0.5 MPa/micrometers to about 0.5MPa/micrometers (indicating a flat or zero slope stress profile alongsuch thickness ranges, as shown in FIG. 3, 220 ). The glass-basedarticles of one or more embodiments of this disclosure do not exhibitsuch a stress profile having a flat or zero slope stress profile alongthese thickness ranges, as shown in FIG. 4 .

In one or more embodiments, the glass-based article exhibits a stressprofile in a thickness range from about 0.1·t to 0.3·t and from about0.7·t to 0.9·t that comprises a maximum tangent and a minimum tangent.In some instances, the difference between the maximum tangent and theminimum tangent is about 3.5 MPa/micrometers or less, about 3MPa/micrometers or less, about 2.5 MPa/micrometers or less, or about 2MPa/micrometers or less.

In one or more embodiments, the glass-based article includes a stressprofile 312 that is substantially free of any linear segments thatextend in a depth direction or along at least a portion of the thicknesst of the glass-based article. In other words, the stress profile 312 issubstantially continuously increasing or decreasing along the thicknesst. In some embodiments, the stress profile is substantially free of anylinear segments in a depth direction having a length of about 10micrometers or more, about 50 micrometers or more, or about 100micrometers or more, or about 200 micrometers or more. As used herein,the term “linear” refers to a slope having a magnitude of less thanabout 5 MPa/micrometer, or less than about 2 MPa/micrometer along thelinear segment. In some embodiments, one or more portions of the stressprofile that are substantially free of any linear segments in a depthdirection are present at depths within the glass-based article of about5 micrometers or greater (e.g., 10 micrometers or greater, or 15micrometers or greater) from either one or both the first surface or thesecond surface. For example, along a depth of about 0 micrometers toless than about 5 micrometers from the first surface, the stress profilemay include linear segments, but from a depth of about 5 micrometers orgreater from the first surface, the stress profile may be substantiallyfree of linear segments.

In some embodiments, the stress profile may include linear segments atdepths from about 0t up to about 0.1t and may be substantially free oflinear segments at depths of about 0.1t to about 0.4t. In someembodiments, the stress profile from a thickness in the range from about0t to about 0.1t may have a slope in the range from about 20 MPa/micronsto about 200 MPa/microns. As will be described herein, such embodimentsmay be formed using a single ion-exchange process by which the bathincludes two or more alkali salts or is a mixed alkali salt bath ormultiple (e.g., 2 or more) ion exchange processes.

In one or more embodiments, the glass-based article may be described interms of the shape of the stress profile along the CT region (327 inFIG. 4 ). For example, in some embodiments, the stress profile along theCT region (where stress is in tension) may be approximated by equation.In some embodiments, the stress profile along the CT region may beapproximated by Equation (1):

Stress(x)=MaxT−(((CT _(n)·(n+1))/0.5^(n))·|(x/t)−0.5|^(m))  (1)

In Equation (1), the stress (x) is the stress value at position x. Herethe stress is positive (tension). In Equation (1), MaxT is the maximumtension value and CT_(n) is the tension value at n and is less than orequal to MaxT. Both MaxT and CT_(n) as positive values in MPa. The valuex is position along the thickness (t) in micrometers, with a range from0 to t; x=0 is one surface (302, in FIG. 4 ), x=0.5t is the center ofthe glass-based article, stress(x)=MaxCT, and x=t is the oppositesurface (304, in FIG. 4 ). MaxT used in Equation (1) is equivalent tothe CT, which may be less than about 71.5/√(t). In some embodiments, theMaxT used in Equation (1) may be in the range from about 50 MPa to about80 MPa (e.g., from about 60 MPa to about 80 MPa, from about 70 MPa toabout 80 MPa, from about 50 MPa to about 75 MPa, from about 50 MPa toabout 70 MPa, or from about 50 MPa to about 65 MPa), and n is a fittingparameter from 1.5 to 5 (e.g., 2 to 4, 2 to 3 or 1.8 to 2.2) or fromabout 1.5 to about 2. In one or more embodiments, n=2 can provide aparabolic stress profile, exponents that deviate from n=2 provide stressprofiles with near parabolic stress profiles. FIG. 5 is a graphillustrating various stress profiles according to one or moreembodiments of this disclosure, based on changes in the fittingparameter n.

In one or more embodiments, CTn may be less than MaxT where there is acompressive stress spike on one or both major surfaces of theglass-based article. In one or more embodiments, CTn is equal to MaxTwhen there is no compressive stress spike on one or both major surfacesof the glass-based article.

In some embodiments, the stress profile may be modified by heattreatment. In such embodiments, the heat treatment may occur before anyion-exchange processes, between ion-exchange processes, or after allion-exchange processes. In some embodiments, the heat treatment mayresult reduce the slope of the stress profile at or near the surface. Insome embodiments, where a steeper or greater slope is desired at thesurface, an ion-exchange process after the heat treatment may beutilized to provide a “spike” or to increase the slope of the stressprofile at or near the surface.

In one or more embodiments, the stress profile 312 (and/or estimatedstress profile 340) is generated due to a non-zero concentration of ametal oxide(s) that varies along a portion of the thickness. Thevariation in concentration may be referred to herein as a gradient. Insome embodiments, the concentration of a metal oxide is non-zero andvaries, both along a thickness range from about 0·t to about 0.3·t. Insome embodiments, the concentration of the metal oxide is non-zero andvaries along a thickness range from about 0·t to about 0.35·t, fromabout 0·t to about 0.4·t, from about 0·t to about 0.45·t or from about0·t to about 0.48·t. The metal oxide may be described as generating astress in the glass-based article. The variation in concentration may becontinuous along the above-referenced thickness ranges. Variation inconcentration may include a change in metal oxide concentration of about0.2 mol % along a thickness segment of about 100 micrometers. Thischange may be measured by known methods in the art including microprobe,as shown in Example 1. The metal oxide that is non-zero in concentrationand varies along a portion of the thickness may be described asgenerating a stress in the glass-based article.

The variation in concentration may be continuous along theabove-referenced thickness ranges. In some embodiments, the variation inconcentration may be continuous along thickness segments in the rangefrom about 10 micrometers to about 30 micrometers. In some embodiments,the concentration of the metal oxide decreases from the first surface toa point between the first surface and the second surface and increasesfrom the point to the second surface.

The concentration of metal oxide may include more than one metal oxide(e.g., a combination of Na₂O and K₂O). In some embodiments, where twometal oxides are utilized and where the radius of the ions differ fromone or another, the concentration of ions having a larger radius isgreater than the concentration of ions having a smaller radius atshallow depths, while the at deeper depths, the concentration of ionshaving a smaller radius is greater than the concentration of ions havinglarger radius. For example, where a single Na− and K− containing bath isused in the ion exchange process, the concentration of K+ ions in theglass-based article is greater than the concentration of Na+ ions atshallower depths, while the concentration of Na+ is greater than theconcentration of K+ ions at deeper depths. This is due, in part, due tothe size of the ions. In such glass-based articles, the area at or nearthe surface comprises a greater CS due to the greater amount of largerions (i.e., K+ ions) at or near the surface. This greater CS may beexhibited by a stress profile having a steeper slope at or near thesurface (i.e., a spike in the stress profile at the surface).

The concentration gradient or variation of one or more metal oxides iscreated by chemically strengthening a glass-based substrate, aspreviously described herein, in which a plurality of first metal ions inthe glass-based substrate is exchanged with a plurality of second metalions. The first ions may be ions of lithium, sodium, potassium, andrubidium. The second metal ions may be ions of one of sodium, potassium,rubidium, and cesium, with the proviso that the second alkali metal ionhas an ionic radius greater than the ionic radius than the first alkalimetal ion. The second metal ion is present in the glass-based substrateas an oxide thereof (e.g., Na₂O, K₂O, Rb₂O, Cs₂O or a combinationthereof).

In one or more embodiments, the metal oxide concentration gradientextends through a substantial portion of the thickness t or the entirethickness t of the glass-based article, including the CT layer 327. Inone or more embodiments, the concentration of the metal oxide is about0.5 mol % or greater in the CT layer 327. In some embodiments, theconcentration of the metal oxide may be about 0.5 mol % or greater(e.g., about 1 mol % or greater) along the entire thickness of theglass-based article, and is greatest at the first surface 302 and/or thesecond surface 304 and decreases substantially constantly to a pointbetween the first surface 302 and the second surface 304. At that point,the concentration of the metal oxide is the least along the entirethickness t; however the concentration is also non-zero at that point.In other words, the non-zero concentration of that particular metaloxide extends along a substantial portion of the thickness t (asdescribed herein) or the entire thickness t. In some embodiments, thelowest concentration in the particular metal oxide is in the CT layer327. The total concentration of the particular metal oxide in theglass-based article may be in the range from about 1 mol % to about 20mol %.

In one or more embodiments, the glass-based article includes a firstmetal oxide concentration and a second metal oxide concentration, suchthat the first metal oxide concentration is in the range from about 0mol % to about 15 mol % along a first thickness range from about 0t toabout 0.5t, and the second metal oxide concentration is in the rangefrom about 0 mol % to about 10 mol % from a second thickness range fromabout 0 micrometers to about 25 micrometers (or from about 0 micrometersto about 12 micrometers); however, the concentration of one or both thefirst metal oxide and the second metal oxide is non-zero along asubstantial portion or the entire thickness of the glass-based article.The glass-based article may include an optional third metal oxideconcentration. The first metal oxide may include Na₂O while the secondmetal oxide may include K₂O.

The concentration of the metal oxide may be determined from a baselineamount of the metal oxide in the glass-based article prior to beingmodified to include the concentration gradient of such metal oxide.

In some embodiments, the stress profile may be modified by heattreatment. In such embodiments, the heat treatment may occur before anyion-exchange processes, between ion-exchange processes, or after allion-exchange processes. In some embodiments, the heat treatment mayresult reduce the slope of the stress profile at or near the surface. Insome embodiments, where a steeper or greater slope is desired at thesurface, an ion-exchange process after the heat treatment may beutilized to provide a “spike” or to increase the slope of the stressprofile at or near the surface.

In one or more embodiments, the stress profile 312 is generated due to anon-zero concentration of a metal oxide(s) that varies along a portionof the thickness. The variation in concentration may be referred toherein as a gradient. In some embodiments, the concentration of a metaloxide is non-zero and varies, both along a thickness range from about0·t to about 0.3·t. In some embodiments, the concentration of the metaloxide is non-zero and varies along a thickness range from about 0·t toabout 0.35·t, from about 0·t to about 0.4·t, from about 0·t to about0.45·t or from about 0·t to about 0.48·t. The metal oxide may bedescribed as generating a stress in the glass-based article. Thevariation in concentration may be continuous along the above-referencedthickness ranges. Variation in concentration may include a change inmetal oxide concentration of about 0.2 mol % along a thickness segmentof about 100 micrometers. This change may be measured by known methodsin the art including microprobe, as shown in Example 1. The metal oxidethat is non-zero in concentration and varies along a portion of thethickness may be described as generating a stress in the glass-basedarticle.

The variation in concentration may be continuous along theabove-referenced thickness ranges. In some embodiments, the variation inconcentration may be continuous along thickness segments in the rangefrom about 10 micrometers to about 30 micrometers. In some embodiments,the concentration of the metal oxide decreases from the first surface toa point between the first surface and the second surface and increasesfrom the point to the second surface.

The concentration of metal oxide may include more than one metal oxide(e.g., a combination of Na₂O and K₂O). In some embodiments, where twometal oxides are utilized and where the radius of the ions differ fromone or another, the concentration of ions having a larger radius isgreater than the concentration of ions having a smaller radius atshallow depths, while the at deeper depths, the concentration of ionshaving a smaller radius is greater than the concentration of ions havinglarger radius. For example, where a single Na− and K− containing bath isused in the ion exchange process, the concentration of K+ ions in theglass-based article is greater than the concentration of Na+ ions atshallower depths, while the concentration of Na+ is greater than theconcentration of K+ ions at deeper depths. This is due, in part, due tothe size of the ions. In such glass-based articles, the area at or nearthe surface comprises a greater CS due to the greater amount of largerions (i.e., K+ ions) at or near the surface. This greater CS may beexhibited by a stress profile having a steeper slope at or near thesurface (i.e., a spike in the stress profile at the surface).

The concentration gradient or variation of one or more metal oxides iscreated by chemically strengthening a glass-based substrate, aspreviously described herein, in which a plurality of first metal ions inthe glass-based substrate is exchanged with a plurality of second metalions. The first ions may be ions of lithium, sodium, potassium, andrubidium. The second metal ions may be ions of one of sodium, potassium,rubidium, and cesium, with the proviso that the second alkali metal ionhas an ionic radius greater than the ionic radius than the first alkalimetal ion. The second metal ion is present in the glass-based substrateas an oxide thereof (e.g., Na₂O, K₂O, Rb₂O, Cs₂O or a combinationthereof).

In one or more embodiments, the metal oxide concentration gradientextends through a substantial portion of the thickness t or the entirethickness t of the glass-based article, including the CT layer 327. Inone or more embodiments, the concentration of the metal oxide is about0.5 mol % or greater in the CT layer 327. In some embodiments, theconcentration of the metal oxide may be about 0.5 mol % or greater(e.g., about 1 mol % or greater) along the entire thickness of theglass-based article, and is greatest at the first surface 302 and/or thesecond surface 304 and decreases substantially constantly to a pointbetween the first surface 302 and the second surface 304. At that point,the concentration of the metal oxide is the least along the entirethickness t; however the concentration is also non-zero at that point.In other words, the non-zero concentration of that particular metaloxide extends along a substantial portion of the thickness t (asdescribed herein) or the entire thickness t. In some embodiments, thelowest concentration in the particular metal oxide is in the CT layer327. The total concentration of the particular metal oxide in theglass-based article may be in the range from about 1 mol % to about 20mol %.

In one or more embodiments, the glass-based article includes a firstmetal oxide concentration and a second metal oxide concentration, suchthat the first metal oxide concentration is in the range from about 0mol % to about 15 mol % along a first thickness range from about 0t toabout 0.5t, and the second metal oxide concentration is in the rangefrom about 0 mol % to about 10 mol % from a second thickness range fromabout 0 micrometers to about 25 micrometers (or from about 0 micrometersto about 12 micrometers); however, the concentration of one or both thefirst metal oxide and the second metal oxide is non-zero along asubstantial portion or the entire thickness of the glass-based article.The glass-based article may include an optional third metal oxideconcentration. The first metal oxide may include Na₂O while the secondmetal oxide may include K₂O.

The concentration of the metal oxide may be determined from a baselineamount of the metal oxide in the glass article prior to being modifiedto include the concentration gradient of such metal oxide.

The glass articles described herein may exhibit a stored tensile energyin the range from greater than 15 J/m² or greater (e.g., from about 15J/m² to about 50 J/m²). For example, in some embodiments, the storedtensile energy may be in the range from about 20 J/m² to about 150 J/m².In some instances, the stored tensile energy may be in the range fromabout 25 J/m² to about 150 J/m², from about 30 J/m² to about 150 J/m²,from about 35 J/m² to about 150 J/m², from about 40 J/m² to about 150J/m², from about 45 J/m² to about 150 J/m², from about 50 J/m² to about150 J/m², from about 55 J/m² to about 150 J/m², from about 60 J/m² toabout 150 J/m², from about 65 J/m² to about 150 J/m², from about 25 J/m²to about 140 J/m², from about 25 J/m² to about 130 J/m², from about 25J/m² to about 120 J/m², from about 25 J/m² to about 110 J/m², from about30 J/m² to about 140 J/m², from about 35 J/m² to about 130 J/m², fromabout 40 J/m² to about 120 J/m² or from about 40 J/m² to about 100 J/m².The thermally and chemically strengthened glass-based articles of one ormore embodiments may exhibit a stored tensile energy of about 40 J/m² orgreater, about 45 J/m² or greater, about 50 J/m² or greater, about 60J/m² or greater, or about 70 J/m² or greater.

Stored tensile energy is calculated using the following Equation (2):

stored tensile energy (J/m²)=[1-ν]/E∫σ{circumflex over ( )}2dt  (2)

where ν is Poisson's ratio, E is the Young's modulus and the integrationis computed for the tensile region only. Equation (2) is described inSuresh T. Gulati, Frangibility of Tempered Soda-Lime Glass Sheet, GLASSPROCESSING DAYS, The Fifth International Conference on Architectural andAutomotive Glass, 13-15 Sep. 1997, as equation number 4.

The glass articles of some embodiments exhibit superior mechanicalperformance as demonstrated by device drop testing or component leveltesting, as compared to known strengthened glass articles. In one ormore embodiments, the glass articles exhibit improved surface strengthwhen subjected to abraded ring-on-ring (AROR) testing. The strength of amaterial is defined as the stress at which fracture occurs. The ARORtest is a surface strength measurement for testing flat glass specimens,and ASTM C1499-09(2013), entitled “Standard Test Method for MonotonicEquibiaxial Flexural Strength of Advanced Ceramics at AmbientTemperature,” serves as the basis for the ring-on-ring abraded ROR testmethodology described herein. The contents of ASTM C1499-09 areincorporated herein by reference in their entirety. In one embodiment,the glass specimen is abraded prior to ring-on-ring testing with 90 gritsilicon carbide (SiC) particles that are delivered to the glass sampleusing the method and apparatus described in Annex A2, entitled “abrasionProcedures,” of ASTM C158-02(2012), entitled “Standard Test Methods forStrength of Glass by Flexure (Determination of Modulus of Rupture). Thecontents of ASTM C158-02 and the contents of Annex 2 in particular areincorporated herein by reference in their entirety.

Prior to ring-on-ring testing a surface of the glass article is abradedas described in ASTM C158-02, Annex 2, to normalize and/or control thesurface defect condition of the sample using the apparatus shown inFigure A2.1 of ASTM C158-02. The abrasive material is typicallysandblasted onto the surface 110 of the glass article at a load orpressure of 15 psi or greater using an air pressure of 304 kPa (44 psi).In some embodiments, the abrasive material may be sandblasted onto thesurface 110 at a load of 20 psi, 25 psi or even 45 psi. After air flowis established, 5 cm³ of abrasive material is dumped into a funnel andthe sample is sandblasted for 5 seconds after introduction of theabrasive material.

For the ring-on-ring test, a glass article having at least one abradedsurface 112 as shown in FIG. 5 is placed between two concentric rings ofdiffering size to determine equibiaxial flexural strength or failureload (i.e., the maximum stress that a material is capable of sustainingwhen subjected to flexure between two concentric rings), as also shownin FIG. 5 . In the abraded ring-on-ring configuration 10, the abradedglass article 110 is supported by a support ring 120 having a diameterD2. A force F is applied by a load cell (not shown) to the surface ofthe glass article by a loading ring 130 having a diameter D1.

The ratio of diameters of the loading ring and support ring D1/D2 may bein a range from about 0.2 to about 0.5. In some embodiments, D1/D2 isabout 0.5. Loading and support rings 130, 120 should be alignedconcentrically to within 0.5% of support ring diameter D2. The load cellused for testing should be accurate to within ±1% at any load within aselected range. In some embodiments, testing is carried out at atemperature of 23±2° C. and a relative humidity of 40±10%.

For fixture design, the radius r of the protruding surface of theloading ring 430, h/2≤r≤3 h/2, where h is the thickness of glass article110. Loading and support rings 130, 120 are typically made of hardenedsteel with hardness HRc>40. ROR fixtures are commercially available.

The intended failure mechanism for the ROR test is to observe fractureof the glass article 110 originating from the surface 130 a within theloading ring 130. Failures that occur outside of this region—i.e.,between the loading rings 130 and support rings 120—are omitted fromdata analysis. Due to the thinness and high strength of the glassarticle 110, however, large deflections that exceed 12 of the specimenthickness h are sometimes observed. It is therefore not uncommon toobserve a high percentage of failures originating from underneath theloading ring 130. Stress cannot be accurately calculated withoutknowledge of stress development both inside and under the ring(collected via strain gauge analysis) and the origin of failure in eachspecimen. AROR testing therefore focuses on peak load at failure as themeasured response.

The strength of glass article depends on the presence of surface flaws.However, the likelihood of a flaw of a given size being present cannotbe precisely predicted, as the strength of glass is statistical innature. A probability distribution can therefore generally be used as astatistical representation of the data obtained.

In some embodiments, the strengthened glass articles described hereinexhibits a equibiaxial flexural strength or failure load of 20 kgf orgreater and up to about 45 kgf as determined by AROR testing using aload of 25 psi or even 45 psi to abrade the surface. In otherembodiments, the surface strength is at least 25 kgf, and in still otherembodiments, at least 30 kgf.

In some embodiments, the strengthened glass articles may exhibitimproved drop performance. As used herein, the drop performance isevaluated by assembling the glass article to a mobile phone device. Insome instances, a number of glass articles may be assembled to identicalmobile phone devices and tested identically. The mobile phone devicewith the glass article assembled thereto is then dropped onto anabrasive paper (which may include Al₂O₃ particles or other abradant) forsuccessive drops starting at a height of 50 cm. As each sample survivesthe drop from a height, the mobile phone device with the sample isdropped again from an increase height until the glass article fracture,at which point the failure height of that sample is recorded as amaximum failure height.

In some embodiments, the glass articles exhibit a maximum failure heightof about 100 cm or greater, when having a thickness of about 1 mm. Insome embodiments, the glass articles exhibit a maximum failure height ofabout 120 cm or greater, about 140 cm or greater, about 150 cm orgreater, about 160 cm or greater, about 180 cm or greater or about 200cm or greater, at a thickness of about 1 mm. The glass articles of oneor more embodiments exhibit a diced fracture pattern after failing atthe failure height. The diced fracture pattern includes exhibiting theaspect ratio described herein.

In one or more embodiments, the glass articles herein exhibit fracturebehavior such that, when the glass article is directly bonded to asubstrate (i.e. a display unit), after the glass article fractures, 50%or more of the cracks are sub-surface cracks (where cracks extend onlypartially through the thickness and arrest below surface. For example,in some instances, the cracks may extend partially through the thicknesst of the glass article, for example, from 0.05t to 0.95t. The percentageof cracks in the glass article that extend only partially through thethickness t may be 50% greater, 60% or greater, 70% or greater, 80% orgreater or 90% or greater.

In some embodiments, the strengthened glass-based articles describedherein may be described in terms of performance in an inverted ball onsandpaper (IBoS) test. The IBoS test is a dynamic component level testthat mimics the dominant mechanism for failure due to damageintroduction plus bending that typically occurs in glass-based articlesthat are used in mobile or hand held electronic devices, asschematically shown in FIG. 6 . In the field, damage introduction (a inFIG. 7 ) occurs on the top surface of the glass-based article. Fractureinitiates on the top surface of the glass-based article and damageeither penetrates the glass-based article (b in FIG. 7 ) or the fracturepropagates from bending on the top surface or from the interior portionsof the glass-based article (c in FIG. 7 ). The IBoS test is designed tosimultaneously introduce damage to the surface of the glass and applybending under dynamic load. In some instances, the glass-based articleexhibits improved drop performance when it includes a compressive stressthan if the same glass-based article does not include a compressivestress.

An IBoS test apparatus is schematically shown in FIG. 6 . Apparatus 500includes a test stand 510 and a ball 530. Ball 530 is a rigid or solidball such as, for example, a stainless steel ball, or the like. In oneembodiment, ball 530 is a 4.2 gram stainless steel ball having diameterof 10 mm. The ball 530 is dropped directly onto the glass-based articlesample 518 from a predetermined height h. Test stand 510 includes asolid base 512 comprising a hard, rigid material such as granite or thelike. A sheet 514 having an abrasive material disposed on a surface isplaced on the upper surface of the solid base 512 such that surface withthe abrasive material faces upward. In some embodiments, sheet 514 issandpaper having a 30 grit surface and, in other embodiments, a 180 gritsurface. The glass-based article sample 518 is held in place above sheet514 by sample holder 515 such that an air gap 516 exists betweenglass-based article sample 518 and sheet 514. The air gap 516 betweensheet 514 and glass-based article sample 518 allows the glass-basedarticle sample 518 to bend upon impact by ball 530 and onto the abrasivesurface of sheet 514. In one embodiment, the glass-based article sample218 is clamped across all corners to keep bending contained only to thepoint of ball impact and to ensure repeatability. In some embodiments,sample holder 514 and test stand 510 are adapted to accommodate samplethicknesses of up to about 2 mm. The air gap 516 is in a range fromabout 50 μm to about 100 μm. Air gap 516 is adapted to adjust fordifference of material stiffness (Young's modulus, Emod), but alsoincludes the Young's modulus and thickness of the sample. An adhesivetape 520 may be used to cover the upper surface of the glass-basedarticle sample to collect fragments in the event of fracture of theglass-based article sample 518 upon impact of ball 530.

Various materials may be used as the abrasive surface. In a oneparticular embodiment, the abrasive surface is sandpaper, such assilicon carbide or alumina sandpaper, engineered sandpaper, or anyabrasive material known to those skilled in the art for havingcomparable hardness and/or sharpness. In some embodiments, sandpaperhaving 30 grit may be used, as it has a surface topography that is moreconsistent than either concrete or asphalt, and a particle size andsharpness that produces the desired level of specimen surface damage.

In one aspect, a method 600 of conducting the IBoS test using theapparatus 500 described hereinabove is shown in FIG. 8 . In Step 610, aglass-based article sample (218 in FIG. 6 ) is placed in the test stand510, described previously and secured in sample holder 515 such that anair gap 516 is formed between the glass-based article sample 518 andsheet 514 with an abrasive surface. Method 600 presumes that the sheet514 with an abrasive surface has already been placed in test stand 510.In some embodiments, however, the method may include placing sheet 514in test stand 510 such that the surface with abrasive material facesupward. In some embodiments (Step 610 a), an adhesive tape 520 isapplied to the upper surface of the glass-based article sample 518 priorto securing the glass-based article sample 518 in the sample holder 510.

In Step 520, a solid ball 530 of predetermined mass and size is droppedfrom a predetermined height h onto the upper surface of the glass-basedarticle sample 518, such that the ball 530 impacts the upper surface (oradhesive tape 520 affixed to the upper surface) at approximately thecenter (i.e., within 1 mm, or within 3 mm, or within 5 mm, or within 10mm of the center) of the upper surface. Following impact in Step 520,the extent of damage to the glass-based article sample 518 is determined(Step 630). As previously described hereinabove, herein, the term“fracture” means that a crack propagates across the entire thicknessand/or entire surface of a substrate when the substrate is dropped orimpacted by an object.

In method 600, the sheet 518 with the abrasive surface may be replacedafter each drop to avoid “aging” effects that have been observed inrepeated use of other types (e.g., concrete or asphalt) of drop testsurfaces.

Various predetermined drop heights h and increments are typically usedin method 600. The test may, for example, utilize a minimum drop heightto start (e.g., about 10-20 cm). The height may then be increased forsuccessive drops by either a set increment or variable increments. Thetest described in method 600 is stopped once the glass-based articlesample 518 breaks or fractures (Step 631). Alternatively, if the dropheight h reaches the maximum drop height (e.g., about 100 cm) withoutfracture, the drop test of method 300 may also be stopped, or Step 520may be repeated at the maximum height until fracture occurs.

In some embodiments, IBoS test of method 600 is performed only once oneach glass-based article sample 518 at each predetermined height h. Inother embodiments, however, each sample may be subjected to multipletests at each height.

If fracture of the glass-based article sample 518 has occurred (Step 631in FIG. 7 ), the IBoS test according to method 600 is ended (Step 640).If no fracture resulting from the ball drop at the predetermined dropheight is observed (Step 632), the drop height is increased by apredetermined increment (Step 634)—such as, for example 5, 10, or 20cm—and Steps 620 and 630 are repeated until either sample fracture isobserved (631) or the maximum test height is reached (636) withoutsample fracture. When either Step 631 or 636 is reached, the testaccording to method 600 is ended.

When subjected to the inverted ball on sandpaper (IBoS) test describedabove, embodiments of the glass-based article described herein have atleast about a 60% survival rate when the ball is dropped onto thesurface of the glass from a height of 100 cm. For example, a glass-basedarticle is described as having a 60% survival rate when dropped from agiven height when three of five identical (or nearly identical) samples(i.e., having approximately the same composition and, when strengthened,approximately the same compressive stress and depth of compression orcompressive stress layer, as described herein) survive the IBoS droptest without fracture when dropped from the prescribed height (here 100cm). In other embodiments, the survival rate in the 100 cm IBoS test ofthe glass-based articles that are strengthened is at least about 70%, inother embodiments, at least about 80%, and, in still other embodiments,at least about 90%. In other embodiments, the survival rate of thestrengthened glass-based articles dropped from a height of 100 cm in theIBoS test is at least about 60%, in other embodiments, at least about70%, in still other embodiments, at least about 80%, and, in otherembodiments, at least about 90%. In one or more embodiments, thesurvival rate of the strengthened glass-based articles dropped from aheight of 150 cm in the IBoS test is at least about 60%, in otherembodiments, at least about 70%, in still other embodiments, at leastabout 80%, and, in other embodiments, at least about 90%.

To determine the survivability rate of the glass-based articles whendropped from a predetermined height using the IBoS test method andapparatus described hereinabove, at least five identical (or nearlyidentical) samples (i.e., having approximately the same composition and,if strengthened, approximately the same compressive stress and depth ofcompression or layer) of the glass-based articles are tested, althoughlarger numbers (e.g., 10, 20, 30, etc.) of samples may be subjected totesting to raise the confidence level of the test results. Each sampleis dropped a single time from the predetermined height (e.g., 100 cm or150 cm) or, alternatively, dropped from progressively higher heightswithout fracture until the predetermined height is reached, and visually(i.e., with the naked eye) examined for evidence of fracture (crackformation and propagation across the entire thickness and/or entiresurface of a sample). A sample is deemed to have “survived” the droptest if no fracture is observed after being dropped from thepredetermined height, and a sample is deemed to have “failed (or “notsurvived”) if fracture is observed when the sample is dropped from aheight that is less than or equal to the predetermined height. Thesurvivability rate is determined to be the percentage of the samplepopulation that survived the drop test. For example, if 7 samples out ofa group of 10 did not fracture when dropped from the predeterminedheight, the survivability rate of the glass would be 70%.

In one or more embodiments, the glass articles exhibit a lower delayedfracture rate (i.e., the glass articles, when fractured, fracturequickly or even immediately). In some embodiments, this fracture ratemay be attributed to the deep DOC and high level of CT. Specifically,there is a lower probability that the glass article will breakspontaneously, well after the insult to the glass article that inducesfracture or failure occurs. In one or more embodiments, when the glassarticle fractures, it fractures into a plurality of fragments within 2seconds or 1 second or less after impact measured by the “FrangibilityTest”, as described Z. Tang, et al. Automated Apparatus for Measuringthe Frangibility and Fragmentation of Strengthened Glass. ExperimentalMechanics (2014) 54:903-912. The Frangibility Test utilizes a dropheight of the stylus of 50 mm and a stylus with a tungsten carbide tip(available from Fisher Scientific Industries, under the trademark TOSCO®and manufacturer identifying number #13-378, with a 60 degreeconi-spherical tip), having a weight of 40 g. In some embodiments, aprimary fracture (or the first fracture visible to the naked eye thatcreates 2 fragments) occurs immediately or within zero seconds or 0.1seconds after an impact that causes the glass article to fracture. Inone or more embodiments, the probability of the primary fractureoccurring within the time periods described herein, as measured by theFrangibility Test, is about 90% or greater In some embodiments,secondary fracture(s) occur within 5 seconds or less (e.g., 4 seconds orless, 3 seconds or less, 2 seconds or less or about 1 second or less).As used herein, “secondary fracture” means a fracture that occurs afterthe primary fracture. In one or more embodiments, the probability of thesecondary fracture(s) occurring within the time periods describedherein, as measured by the Frangibility Test, is about 90% or greater.

In one or more embodiments, upon fracturing, the glass article ejectsfewer and smaller fragments that are of potential concern to a user thanis exhibited by known glass articles currently being used on mobileelectronic devices. As used herein, the term “ejects” or “ejected”refers to fragments that move from their original position or placementin the glass article after the glass article is fractured. In someembodiments, after the glass article is fractured and a plurality offragments is formed, about 10% or less (e.g., about 8% or less, about 6%or less, or about 5% or less) of the plurality of fragments is ejected.In some embodiments, after the glass article is fractured and aplurality of fragments is formed, about 50% of more of the ejectedportion of the plurality of fragments has a maximum dimension less than0.5 mm. In some embodiments, the number or amount of ejected fragmentsmay be characterized by weight, in relation to the glass article beforeand after fracture. For example, the difference between the weight ofthe glass article prior to fracture (including the total weight of theejected portion of the plurality of fragments and the non-ejectedportion of fragments, after fracture) and the weight of the non-ejectedportion of fragments, may be less than about 1% or less of the weightprior to impact. In some instances, difference between the weight of theglass article prior to fracture (including the total weight of theejected portion of the plurality of fragments and the non-ejectedportion of fragments, after fracture) and the weight of the non-ejectedportion of fragments, may be less than about 0.0005 g (e.g., 0.0004 g orless, 0.0003 g or less, 0.0002 g or less, or 0.0001 g or less). Todetermine the weight of the non-ejected portion.

In one or more embodiments, the glass article exhibits a high degree ofdicing in a more uniform pattern across the surface and volume thereof.In some embodiments, this high degree of dicing and uniformity isexhibited where the glass article has a non-uniform thickness (i.e., isshaped to have a three-dimensional or 2.5 dimensional shape). Withoutbeing bound by theory, this enables the thinnest portion of the glassarticle to be strengthened to a sufficient degree, without having someportions of the glass article exhibiting frangibility while otherportions are non-frangible, as defined by current industry norms.

In one or more embodiments, the glass article (directly bonded to thesubstrate, i.e., a display unit) exhibits a haze after being fractured,due to the dense fracture pattern. The readability of depends on viewingangle and the thickness of the glass-based article. At a viewing angleof 90 degrees to a major surface of the glass article or at normalincidence, the fractured glass article exhibits a low haze such that anunderlying image or text is visible to the naked eye. At a viewing angleof 70 degrees or less to a major surface of the glass article (or 30degrees or more away from normal incidence), the fractured glass articleexhibits a haze that prevents the underlying image or text from beingvisible to the naked eye. It should be understood that such haze ispresent when the fragments of the glass article are still held togetheror when less than 10% of the fragments are ejected from the glassarticle. Without being bound by theory, it is believed that the glassarticle after fracture may provide privacy screen functionality due toits low haze at 90 degrees and the high haze at smaller viewing angles.

In some embodiments, at least one major surface of the glass article hasa low surface roughness after the glass article is fractured. Thisattribute is desirable where the glass article may be used or touched bya user even after the glass article is fractured so that cuts andabrasions to the user are minimized or eliminated.

In one or more embodiments, the glass articles described herein may becombined with a containment layer. The containment layer is a materialthat can contain the fragments of the glass article, when fractured. Forexample, the containment layer may include a polymeric material. In oneor more embodiments, the containment layer may include an adhesivematerial (such as a pressure-sensitive adhesive material). In one ormore embodiments, the containment layer may have a Young's modulus inthe range from about 0.5 to about 1.2 MPa. In one or more embodiments,the containment layer may include a filled epoxy, an unfilled epoxy, afilled urethane or an unfilled urethane.

An example of a filled epoxy includes a UV induced catiltic epoxy fromthe polymerization product of 70.69 wt % Nanopox C620 colloidal silicasol (40% silica nanoparticles in cycloaliphatic epoxy resin), 23.56 wt %Nanopox C680 (50% wt silica nanoparticles in3-ethyl-3-hydroxymethyl-oxetane), 3 wt % Coatosil MP-200 epoxyfunctional silane (adhesion promoter), 2.5 wt % Cyracril UVI-6976(cationic photoinitiator, including triarylsulfoniumhexaflouroantimonate salts in propylene carbonate), 0.25 wt % Tinuvine292 amine stabilizer (bis(1,2,2,6,6-pentamethyl-4-piperidinyl)-sebacateand 1-(methyl)−8-(1,2,2,6,6-pentamethyl-4-piperidinyl)-sebacate),

An example of an unfilled epoxy material includes 48 wt % Synasia S06Ecycloaliphatic epoxy, 48 wt % Synasia S-101 (3-ethyl-3-oxetanemethanol),1 wt % UVI-6976 (cationic photoinitiator), and 3 wt % Silquest A-186(epoxy functionalized silane).

In some embodiments, a low modulus urethane acrylate can be used in thecontainment layer. In some embodiments, this material may include silicafilling. An example of a low modulus urethane acrylate includes 31.5 wt% Doublemer 554 (aliphatic urethane diacrylate resin), 1.5 wt % Genomer4188/M22 (monofunctional urethane acrylate), 20 wt % NK Ester A-SA(beta-acryloyl oxyethyl hydrogen succinate), 10 wt % Sartomer SR339 2(phenoxyethyl acrylate), 4 wt % Irgacure 2022 (photoinitiator, acylphosphine oxide/alpha hydroxy ketone), 3 wt % adhesion promoter (e.g.,Silquest A-189, gamma-mercaptopropyltrimethoxysilane). To form a filledurethane, 4 wt % silica powder (such as Hi Sil 233) may be added.

In one or more embodiments, the glass article may be combined with acontainment layer with or without being adhered thereto. In someembodiments, the glass articles may be disposed on and adhered to acontainment layer. The glass article may be temporarily adhered orpermanently adhered to a containment layer. As shown in FIG. 9A, thecontainment layer 20 is disposed on at least one major surface (e.g.,12, 14, in FIG. 1A) of the glass article. In FIG. 9A, the containmentlayer 20 is not disposed on any portion of the minor surfaces 16, 18;however, the containment layer 20 may extend from the major surface toat least partially along one or both minor surfaces (16, 18) or alongthe entire length of one or both minor surfaces (16, 18). In suchembodiments, the containment layer may be formed from the same material.In one or more alternative embodiments, the containment layer formed onthe major surface may be different from the containment layer formed onany portion of the minor surface(s). FIG. 9B illustrates an embodimentin which the containment layer 20 is disposed on the major surface 14and a second containment layer 22 is disposed on both minor surfaces 16,18. In one or more embodiment, the containment layer 20 differscompositionally from the second containment layer 22.

In one or more embodiments, the glass article may include a stressprofile including a spike, as described herein, such that the surface CSis in the range from about 400 MPa to about 1200 MPa and includes acontainment material 20 on one major surface 14, and a secondcontainment material 22 on both minor surfaces 16, 18 (as shown in FIG.9B). In one or more embodiments, the glass article may include a stressprofile without a spike, such that the surface CS is in the range fromabout 150 MPa to about 500 MPa, and includes only containment material20 on major surface 14 (as shown in FIG. 9A).

The glass articles described herein may be incorporated into variousproducts and articles such as in consumer electronics products ordevices (e.g., cover glass for mobile electronic devices andtouch-enabled displays). The glass articles may also be used in displays(or as display articles) (e.g., billboards, point of sale systems,computers, navigation systems, and the like), architectural articles(walls, fixtures, panels, windows, etc.), transportation articles (e.g.,in automotive applications, trains, aircraft, sea craft, etc.),appliances (e.g., washers, dryers, dishwashers, refrigerators and thelike), packaging (e.g., pharmaceutical packaging or containers) or anyarticle that requires some fracture resistance.

As shown in FIG. 10 , an electronic device 1000 may include aglass-based article 100 according to one or more embodiments describedherein. The device 100 includes a housing 1020 having front 1040, back1060, and side surfaces 1080; electrical components (not shown) that areat least partially inside or entirely within the housing and includingat least a controller, a memory, and a display 1120 at or adjacent tothe front surface of the housing. The glass-based article 100 is shownas a cover disposed at or over the front surface of the housing suchthat it is over the display 1120. In some embodiments, the glass-basedarticle may be used as a back cover.

In some embodiments, the electronic device may include a tablet, atransparent display, a mobile phone, a video player, an informationterminal device, an e-reader, a laptop computer, or a non-transparentdisplay.

In one or more embodiments, the glass articles described herein may beused in packaging. For example, the packaging may include glass articlesin the form of bottles, vials or containers that hold a liquid, solid orgas material. In one or more embodiments, the glass articles are vialsthat include chemicals such as pharmaceutical materials. In one or moreembodiments, the packaging includes a housing including an opening, anexterior surface and an interior surface defining an enclosure. Thehousing may be formed from the glass articles described herein. Theglass article includes a containment layer. In some embodiments, theenclosure is filled with a chemical or pharmaceutical material. In oneor more embodiments, the opening of the housing may be closed or sealedby a cap. In other words, the cap may be disposed in the opening toclose or seal the enclosure.

The glass article may include an amorphous substrate, a crystallinesubstrate or a combination thereof (e.g., a glass-ceramic substrate).The glass article may include an alkali aluminosilicate glass, alkalicontaining borosilicate glass, alkali aluminophosphosilicate glass oralkali aluminoborosilicate glass. In one or more embodiments, the glassarticle substrate (prior to being chemically strengthened as describedherein) may include a glass having a composition, in mole percent (mole%), including: SiO2 in the range from about 40 to about 80, Al₂O₃ in therange from about 10 to about 30, B₂O₃ in the range from about 0 to about10, R₂O in the range from about 0 to about 20, and RO in the range fromabout 0 to about 15. In some instances, the composition may includeeither one or both of ZrO₂ in the range from about 0 mol % to about 5mol % and P₂O₅ in the range from about 0 to about 15 mol %. TiO₂ can bepresent from about 0 mol % to about 2 mol %.

In some embodiments, the glass composition may include SiO₂ in anamount, in mol %, in the range from about 45 to about 80, from about 45to about 75, from about 45 to about 70, from about 45 to about 65, fromabout 45 to about 60, from about 45 to about 65, from about 45 to about65, from about 50 to about 70, from about 55 to about 70, from about 60to about 70, from about 70 to about 75, or from about 50 to about 65.

In some embodiments, the glass composition may include Al₂O₃ in anamount, in mol %, in the range from about 5 to about 28, from about 5 toabout 26, from about 5 to about 25, from about 5 to about 24, from about5 to about 22, from about 5 to about 20, from about 6 to about 30, fromabout 8 to about 30, from about 10 to about 30, from about 12 to about30, from about 14 to about 30, from about 16 to about 30, from about 18to about 30, or from about 18 to about 28.

In one or more embodiments, the glass composition may include B₂O₃ in anamount, in mol %, in the range from about 0 to about 8, from about 0 toabout 6, from about 0 to about 4, from about 0.1 to about 8, from about0.1 to about 6, from about 0.1 to about 4, from about 1 to about 10,from about 2 to about 10, from about 4 to about 10, from about 2 toabout 8, from about 0.1 to about 5, or from about 1 to about 3. In someinstances, the glass composition may be substantially free of B₂O₃. Asused herein, the phrase “substantially free” with respect to thecomponents of the composition means that the component is not activelyor intentionally added to the composition during initial batching, butmay be present as an impurity in an amount less than about 0.001 mol %.

In some embodiments, the glass composition may include one or morealkali earth metal oxides, such as MgO, CaO and ZnO. In someembodiments, the total amount of the one or more alkali earth metaloxides may be a non-zero amount up to about 15 mol %. In one or morespecific embodiments, the total amount of any of the alkali earth metaloxides may be a non-zero amount up to about 14 mol %, up to about 12 mol%, up to about 10 mol %, up to about 8 mol %, up to about 6 mol %, up toabout 4 mol %, up to about 2 mol %, or up about 1.5 mol %. In someembodiments, the total amount, in mol %, of the one or more alkali earthmetal oxides may be in the range from about 0.1 to 10, from about 0.1 to8, from about 0.1 to 6, from about 0.1 to 5, from about 1 to 10, fromabout 2 to 10, or from about 2.5 to 8. The amount of MgO may be in therange from about 0 mol % to about 5 mol % (e.g., from about 2 mol % toabout 4 mol %). The amount of ZnO may be in the range from about 0 toabout 2 mol %. The amount of CaO may be from about 0 mol % to about 2mol %. In one or more embodiments, the glass composition may include MgOand may be substantially free of CaO and ZnO. In one variant, the glasscomposition may include any one of CaO or ZnO and may be substantiallyfree of the others of MgO, CaO and ZnO. In one or more specificembodiments, the glass composition may include only two of the alkaliearth metal oxides of MgO, CaO and ZnO and may be substantially free ofthe third of the earth metal oxides.

The total amount, in mol %, of alkali metal oxides R₂O in the glasscomposition may be in the range from about 5 to about 20, from about 5to about 18, from about 5 to about 16, from about 5 to about 15, fromabout 5 to about 14, from about 5 to about 12, from about 5 to about 10,from about 5 to about 8, from about 5 to about 20, from about 6 to about20, from about 7 to about 20, from about 8 to about 20, from about 9 toabout 20, from about 10 to about 20, from about 6 to about 13, or fromabout 8 to about 12.

In one or more embodiments, the glass composition includes Na₂O in anamount in the range from about 0 mol % to about 18 mol %, from about 0mol % to about 16 mol % or from about 0 mol % to about 14 mol %, fromabout 0 mol % to about 10 mol %, from about 0 mol % to about 5 mol %,from about 0 mol % to about 2 mol %, from about 0.1 mol % to about 6 mol%, from about 0.1 mol % to about 5 mol %, from about 1 mol % to about 5mol %, from about 2 mol % to about 5 mol %, or from about 10 mol % toabout 20 mol %.

In some embodiments, the amount of Li₂O and Na₂O is controlled to aspecific amount or ratio to balance formability and ion exchangeability.For example, as the amount of Li₂O increases, the liquidus viscosity maybe reduced, thus preventing some forming methods from being used;however, such glass compositions are ion exchanged to deeper DOC levels,as described herein. The amount of Na₂O can modify liquidus viscositybut can inhibit ion exchange to deeper DOC levels.

In one or more embodiments, the glass composition may include K₂O in anamount less than about 5 mol %, less than about 4 mol %, less than about3 mol %, less than about 2 mol %, or less than about 1 mol %. In one ormore alternative embodiments, the glass composition may be substantiallyfree, as defined herein, of K₂O.

In one or more embodiments, the glass composition may include Li₂O in anamount about 0 mol % to about 18 mol %, from about 0 mol % to about 15mol % or from about 0 mol % to about 10 mol %, from about 0 mol % toabout 8 mol %, from about 0 mol % to about 6 mol %, from about 0 mol %to about 4 mol % or from about 0 mol % to about 2 mol %. In someembodiments, the glass composition may include Li₂O in an amount about 2mol % to about 10 mol %, from about 4 mol % to about 10 mol %, fromabout 6 mol % to about 10 mol, or from about 5 mol % to about 8 mol %.In one or more alternative embodiments, the glass composition may besubstantially free, as defined herein, of Li₂O.

In one or more embodiments, the glass composition may include Fe₂O₃. Insuch embodiments, Fe₂O₃ may be present in an amount less than about 1mol %, less than about 0.9 mol %, less than about 0.8 mol %, less thanabout 0.7 mol %, less than about 0.6 mol %, less than about 0.5 mol %,less than about 0.4 mol %, less than about 0.3 mol %, less than about0.2 mol %, less than about 0.1 mol % and all ranges and sub-rangestherebetween. In one or more alternative embodiments, the glasscomposition may be substantially free, as defined herein, of Fe₂O₃.

In one or more embodiments, the glass composition may include ZrO₂. Insuch embodiments, ZrO₂ may be present in an amount less than about 1 mol%, less than about 0.9 mol %, less than about 0.8 mol %, less than about0.7 mol %, less than about 0.6 mol %, less than about 0.5 mol %, lessthan about 0.4 mol %, less than about 0.3 mol %, less than about 0.2 mol%, less than about 0.1 mol % and all ranges and sub-ranges therebetween.In one or more alternative embodiments, the glass composition may besubstantially free, as defined herein, of ZrO₂.

In one or more embodiments, the glass composition may include P₂O₅ in arange from about 0 mol % to about 10 mol %, from about 0 mol % to about8 mol %, from about 0 mol % to about 6 mol %, from about 0 mol % toabout 4 mol %, from about 0.1 mol % to about 10 mol %, from about 0.1mol % to about 8 mol %, from about 4 mol % to about 8 mol %, or fromabout 5 mol % to about 8 mol %. In some instances, the glass compositionmay be substantially free of P₂O₅.

In one or more embodiments, the glass composition may include TiO₂. Insuch embodiments, TiO₂ may be present in an amount less than about 6 mol%, less than about 4 mol %, less than about 2 mol %, or less than about1 mol %. In one or more alternative embodiments, the glass compositionmay be substantially free, as defined herein, of TiO₂. In someembodiments, TiO₂ is present in an amount in the range from about 0.1mol % to about 6 mol %, or from about 0.1 mol % to about 4 mol %. Insome embodiments, the glass may be substantially free of TiO₂.

In some embodiments, the glass composition may include variouscompositional relationships. For example, the glass composition mayinclude a ratio of the amount of Li₂O (in mol %) to the total amount ofR₂O (in mol %) in the range from about 0.5 to about 1. In someembodiments, the glass composition may include a difference between thetotal amount of R₂O (in mol %) to the amount of Al₂O₃ (in mol %) in therange from about −5 to about 0. In some instances the glass compositionmay include a difference between the total amount of R_(x)O (in mol %)and the amount of Al₂O₃ in the range from about 0 to about 3. The glasscomposition of one or more embodiments may exhibit a ratio of the amountof MgO (in mol %) to the total amount of RO (in mol %) in the range fromabout 0 to about 2.

In some embodiments, the compositions used for the glass substrate maybe batched with 0-2 mol % of at least one fining agent selected from agroup that includes Na₂SO₄, NaCl, NaF, NaBr, K₂SO₄, KCl, KF, KBr, andSnO₂. The glass composition according to one or more embodiments mayfurther include SnO₂ in the range from about 0 to about 2, from about 0to about 1, from about 0.1 to about 2, from about 0.1 to about 1, orfrom about 1 to about 2. The glass compositions disclosed herein may besubstantially free of As₂O₃ and/or Sb₂O₃.

In one or more embodiments, the composition may specifically include 62mol % to 75 mol % SiO₂; 10.5 mol % to about 17 mol % Al₂O₃; 5 mol % toabout 13 mol % Li₂O; 0 mol % to about 4 mol % ZnO; 0 mol % to about 8mol % MgO; 2 mol % to about 5 mol % TiO₂; 0 mol % to about 4 mol % B₂O3;0 mol % to about 5 mol % Na₂O; 0 mol % to about 4 mol % K₂O; 0 mol % toabout 2 mol % ZrO₂; 0 mol % to about 7 mol % P₂O₅; 0 mol % to about 0.3mol % Fe₂O₃; 0 mol % to about 2 mol % MnOx; and 0.05 mol % to about 0.2mol % SnO₂.

In one or more embodiments, the composition may include 67 mol % toabout 74 mol % SiO₂; 11 mol % to about 15 mol % Al₂O₃; 5.5 mol % toabout 9 mol % Li₂O; 0.5 mol % to about 2 mol % ZnO; 2 mol % to about 4.5mol % MgO; 3 mol % to about 4.5 mol % TiO₂; 0 mol % to about 2.2 mol %B₂O3; 0 mol % to about 1 mol % Na₂O; 0 mol % to about 1 mol % K₂O; 0 mol% to about 1 mol % ZrO₂; 0 mol % to about 4 mol % P₂O₅; 0 mol % to about0.1 mol % Fe₂O3; 0 mol % to about 1.5 mol % MnOx; and 0.08 mol % toabout 0.16 mol % SnO₂.

In one or more embodiments, the composition may include 70 mol % to 75mol % SiO₂; 10 mol % to about 15 mol % Al₂O₃; 5 mol % to about 13 mol %Li₂O; 0 mol % to about 4 mol % ZnO; 0.1 mol % to about 8 mol % MgO; 0mol % to about 5 mol % TiO₂; 0.1 mol % to about 4 mol % B₂O3; 0.1 mol %to about 5 mol % Na₂O; 0 mol % to about 4 mol % K₂O; 0 mol % to about 2mol % ZrO₂; 0 mol % to about 7 mol % P₂O₅; 0 mol % to about 0.3 mol %Fe₂O3; 0 mol % to about 2 mol % MnOx; and 0.05 mol % to about 0.2 mol %SnO₂.

In one or more embodiments, the composition may include 52 mol % toabout 63 mol % SiO₂; 11 mol % to about 15 mol % Al₂O₃; 5.5 mol % toabout 9 mol % Li₂O; 0.5 mol % to about 2 mol % ZnO; 2 mol % to about 4.5mol % MgO; 3 mol % to about 4.5 mol % TiO₂; 0 mol % to about 2.2 mol %B₂O3; 0 mol % to about 1 mol % Na₂O; 0 mol % to about 1 mol % K₂O; 0 mol% to about 1 mol % ZrO₂; 0 mol % to about 4 mol % P₂O₅; 0 mol % to about0.1 mol % Fe₂O3; 0 mol % to about 1.5 mol % MnOx; and 0.08 mol % toabout 0.16 mol % SnO₂.

In some embodiments, the composition may be substantially free of anyone or more of B₂O₃, TiO₂, K₂O and ZrO₂.

In one or more embodiments, the composition may include at least 0.5 mol% P₂O₅, Na₂O and, optionally, Li₂O, where Li₂O(mol %)/Na₂O(mol %)<1. Inaddition, these compositions may be substantially free of B₂O₃ and K₂O.In some embodiments, the composition may include ZnO, MgO, and SnO₂.

In some embodiments, the composition may comprise: from about 58 mol %to about 65 mol % SiO₂; from about 11 mol % to about 19 mol % Al₂O₃;from about 0.5 mol % to about 3 mol % P₂O₅; from about 6 mol % to about18 mol % Na₂O; from 0 mol % to about 6 mol % MgO; and from 0 mol % toabout 6 mol % ZnO. In certain embodiments, the composition may comprisefrom about 63 mol % to about 65 mol % SiO₂; from 11 mol % to about 17mol % Al₂O₃; from about 1 mol % to about 3 mol % P₂O₅; from about 9 mol% to about 20 mol % Na₂O; from 0 mol % to about 6 mol % MgO; and from 0mol % to about 6 mol % ZnO.

In some embodiments, the composition may include the followingcompositional relationships R₂O(mol %)/Al₂O₃(mol %)<2, whereR₂O=Li₂O+Na₂O. In some embodiments, 65 mol %<SiO₂(mol %)+P₂O₅(mol %)<67mol %. In certain embodiments, R₂O(mol %)+R′O(mol %)−Al₂O₃(mol%)+P₂O₅(mol %)>−3 mol %, where R₂O=Li₂O+Na₂O and R′O is the total amountof divalent metal oxides present in the composition.

Other exemplary compositions of glass articles prior to being chemicallystrengthened, as described herein, are shown in Table 1.

TABLE 1 Exemplary compositions prior to chemical strengthening. Mol %Ex. A Ex. B Ex. C Ex. D Ex. E Ex. F SiO₂ 71.8 69.8 69.8 69.8 69.8 69.8Al₂O₃ 13.1 13 13 13 13 13 B₂O₃ 2 2.5 4 2.5 2.5 4 Li₂O 8 8.5 8 8.5 8.5 8MgO 3 3.5 3 3.5 1.5 1.5 ZnO 1.8 2.3 1.8 2.3 2.3 1.8 Na₂O 0.4 0.4 0.4 0.40.4 0.4 TiO₂ 0 0 0 1 1 1 Fe₂O₃ 0 0 0 0.8 0.8 0.8 SnO₂ 0.1 0.1 0.1 0.10.1 0.1 Mol % Ex. G Ex. H Ex. I Ex. J Ex. K Ex. L Ex. M Ex. N SiO₂ 70.1870.91 71.28 71.65 71.65 71.65 74.77 72.00 Al₂O₃ 12.50 12.78 12.93 13.0713.07 13.07 10.00 12.50 B₂O₃ 1.91 1.95 1.98 2.00 2.00 2.00 1.99 2.00Li₂O 7.91 7.95 7.96 7.98 6.98 5.00 6.13 6.00 Na₂O 4.43 2.43 1.42 0.411.41 3.40 3.97 0.50 MgO 2.97 2.98 2.99 3.00 3.00 3.00 2.94 2.10 ZnO 0.000.89 1.34 1.80 1.80 1.80 0.00 0.00 CaO 0.00 0.00 0.00 0.00 0.00 0.000.05 4.90 SnO₂ 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 Li₂O/R₂O 0.640.77 0.85 0.95 0.83 0.60 0.61 0.92 R₂O − −0.16 −2.41 −3.54 −4.68 −4.68−4.67 0.10 −6.00 Al₂O₃ R_(x)O − 2.81 1.47 0.79 0.12 0.12 0.13 3.09 1.00Al₂O₃ MgO/RO 1.00 0.77 0.69 0.63 0.63 0.63 1.00 1.00 R₂O 12.34 10.389.39 8.39 8.39 8.40 10.10 6.50 RO 2.97 3.88 4.34 4.79 4.79 4.79 2.997.00

Other exemplary compositions of glass-based articles prior to beingchemically strengthened, as described herein, are shown in Table 1A.Table 1B lists selected physical properties determined for the exampleslisted in Table 1A. The physical properties listed in Table 1B include:density; low temperature and high temperature CTE; strain, anneal andsoftening points; 10¹¹ Poise, 35 kP, 200 kP, liquidus, and zirconbreakdown temperatures; zircon breakdown and liquidus viscosities;Poisson's ratio; Young's modulus; refractive index, and stress opticalcoefficient. In some embodiments, the glass-based articles and glasssubstrates described herein have a high temperature CTE of less than orequal to 30 ppm/° C. and/or a Young's modulus of at least 70 GPa and, insome embodiments, a Young's modulus of up to 80 GPa.

TABLE 1A Exemplary compositions prior to chemical strengthening.Composition (mol %) Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 SiO₂ 63.7764.03 63.67 63.91 64.16 63.21 63.50 Al₂O₃ 12.44 12.44 11.83 11.94 11.9411.57 11.73 P₂O₅ 2.43 2.29 2.36 2.38 1.92 1.93 1.93 Li₂O 0.00 0.00 0.000.00 0.00 0.00 0.00 Na₂O 16.80 16.81 16.88 16.78 16.80 17.63 16.85 ZnO0.00 4.37 0.00 4.93 0.00 5.59 5.93 MgO 4.52 0.02 5.21 0.02 5.13 0.020.01 SnO₂ 0.05 0.05 0.05 0.05 0.05 0.05 0.05 R₂O/Al₂O₃ 1.35 1.35 1.431.41 1.41 1.52 1.44 Li₂O/Na₂O 0.00 0.00 0.00 0.00 0.00 0.00 0.00 (R₂O +RO) − 6.45 6.46 7.89 7.40 8.07 9.74 9.14 Al₂O₃ − P₂O₅ Composition (mol%) Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. 13 Ex. 14 SiO₂ 63.37 63.43 63.5663.58 63.66 63.62 63.67 Al₂O₃ 11.72 12.49 12.63 12.59 12.91 12.85 12.89P₂O₅ 2.00 2.32 2.46 2.46 2.43 2.45 2.47 Li₂O 0.00 0.00 1.42 2.87 0.001.42 2.92 Na₂O 16.84 17.16 15.45 14.04 16.89 15.48 13.92 ZnO 6.00 4.544.43 4.41 4.04 4.12 4.06 MgO 0.02 0.02 0.02 0.02 0.02 0.02 0.02 SnO₂0.05 0.04 0.05 0.05 0.05 0.05 0.05 R₂O/Al₂O₃ 1.44 1.37 1.34 1.34 1.311.31 1.31 Li₂O/Na₂O 0.00 0.00 0.09 0.20 0.00 0.09 0.21 (R₂O + RO) − 9.146.90 6.22 6.29 5.62 5.72 5.57 Al₂O₃ − P₂O₅ Composition (mol %) Ex. 15Ex. 16 Ex. 17 Ex. 18 Ex. 19 Ex. 20 Ex. 21 SiO₂ 63.55 63.80 63.76 63.8863.74 64.03 63.68 Al₂O₃ 12.92 12.90 12.95 13.48 13.37 13.26 13.19 P₂O₅2.35 2.34 2.37 2.31 2.34 2.29 2.46 Li₂O 0.00 1.47 2.94 0.00 1.48 2.940.00 Na₂O 17.97 16.36 14.85 17.20 15.96 14.37 16.84 ZnO 0.00 0.00 0.000.00 0.00 0.00 3.77 MgO 3.17 3.08 3.09 3.08 3.08 3.06 0.02 SnO₂ 0.050.04 0.05 0.05 0.04 0.04 0.05 R₂O/Al₂O₃ 1.39 1.38 1.37 1.28 1.30 1.311.28 Li₂O/Na₂O 0.00 0.09 0.20 0.00 0.09 0.20 0.00 (R₂O + RO) − 5.87 5.675.56 4.48 4.81 4.83 4.98 Al₂O₃ − P₂O₅ Composition (mol %) Ex. 22 Ex. 23Ex. 24 Ex. 25 Ex. 26 Ex. 27 Ex. 28 SiO₂ 63.66 63.76 63.67 63.73 63.7363.64 63.76 Al₂O₃ 14.15 15.31 13.87 14.82 12.93 16.62 16.59 P₂O₅ 2.472.44 2.47 2.43 2.48 2.47 2.47 Li₂O 1.49 2.98 1.50 2.96 0.00 2.52 4.91Na₂O 15.31 13.79 15.36 13.93 16.83 14.68 12.20 ZnO 2.85 1.64 0.00 0.002.98 0.00 0.00 MgO 0.03 0.03 3.09 2.08 1.00 0.03 0.03 SnO₂ 0.05 0.040.05 0.05 0.05 0.05 0.05 R₂O/Al₂O₃ 1.19 1.10 1.22 1.14 1.30 1.03 1.03Li₂O/Na₂O 0.10 0.22 0.10 0.21 0.00 0.17 0.40 (R₂O + RO) − 3.05 0.70 3.611.72 5.40 −1.86 −1.92 Al₂O₃ − P₂O₅ Composition (mol %) Ex. 29 Ex. 30 Ex.31 Ex. 32 Ex. 33 Ex. 34 Ex. 35 SiO₂ 63.89 63.92 63.77 63.73 63.70 63.6563.87 Al₂O₃ 16.55 15.29 15.27 15.30 15.27 15.22 15.29 P₂O₅ 2.47 2.242.31 2.39 2.40 2.48 2.37 Li₂O 7.27 3.46 2.98 4.02 4.46 4.96 5.39 Na₂O9.74 13.46 13.99 12.91 12.51 11.99 11.44 ZnO 0.00 1.56 1.61 1.57 1.581.63 1.57 MgO 0.03 0.02 0.02 0.03 0.03 0.02 0.02 SnO₂ 0.04 0.04 0.040.05 0.04 0.05 0.04 R₂O/Al₂O₃ 1.03 1.11 1.11 1.11 1.11 1.11 1.10Li₂O/Na₂O 0.75 0.26 0.21 0.31 0.36 0.41 0.47 (R₂O + RO) − −1.98 0.971.01 0.84 0.90 0.91 0.76 Al₂O₃ − P₂O₅ Composition (mol %) Ex. 36 Ex. 37Ex. 38 Ex. 39 Ex. 40 Ex. 41 Ex. 42 SiO₂ 63.69 63.75 63.70 63.62 63.7463.77 63.77 Al₂O₃ 15.26 15.30 15.27 15.23 15.27 15.27 15.33 P₂O₅ 2.452.42 2.45 2.46 2.47 2.46 2.44 Li₂O 2.96 2.98 3.94 3.98 4.93 4.93 2.91Na₂O 13.50 13.46 12.54 12.57 11.49 11.50 13.94 ZnO 2.06 2.01 2.03 2.062.03 2.00 0.00 MgO 0.02 0.03 0.02 0.03 0.03 0.03 1.57 SnO₂ 0.05 0.040.04 0.05 0.04 0.05 0.04 R₂O/Al₂O₃ 1.08 1.08 1.08 1.09 1.08 1.08 1.10Li₂O/Na₂O 0.22 0.22 0.31 0.32 0.43 0.43 0.21 (R₂O + RO) − 0.83 0.77 0.800.95 0.73 0.73 0.66 Al₂O₃ − P₂O₅ Composition (mol %) Ex. 43 Ex. 44 Ex.45 Ex. 46 Ex. 47 Ex. 48 Ex. 49 SiO₂ 63.69 63.81 63.65 63.71 63.62 63.6563.62 Al₂O₃ 15.25 15.26 15.33 15.32 15.24 15.68 15.67 P₂O₅ 2.43 2.412.46 2.44 2.47 2.44 2.48 Li₂O 4.00 4.89 2.96 4.01 4.91 6.07 6.06 Na₂O13.01 12.03 13.29 12.25 11.42 10.93 10.53 ZnO 0.00 0.00 2.24 2.20 2.271.17 1.57 MgO 1.57 1.56 0.03 0.03 0.02 0.02 0.02 SnO₂ 0.05 0.04 0.050.04 0.05 0.04 0.05 R₂O/Al₂O₃ 1.12 1.11 1.06 1.06 1.07 1.08 1.06Li₂O/Na₂O 0.31 0.41 0.22 0.33 0.43 0.56 0.58 (R₂O + RO) − 0.90 0.81 0.730.73 0.91 0.08 0.04 Al₂O₃ − P₂O₅ Composition (mol %) Ex. 50 Ex. 51 Ex.52 Ex. 53 Ex. 54 Ex. 55 Ex. 56 SiO₂ 63.60 63.89 63.84 63.90 63.88 64.7460.17 Al₂O₃ 15.65 16.09 16.47 16.87 16.97 15.25 18.58 P₂O₅ 2.46 2.422.43 2.43 2.42 0.98 1.90 Li₂O 6.13 6.80 7.84 8.75 9.78 5.28 5.16 Na₂O10.29 9.97 8.96 7.99 6.88 12.09 12.58 ZnO 1.81 0.78 0.39 0.00 0.00 1.611.55 MgO 0.02 0.02 0.02 0.02 0.02 0.02 0.02 SnO₂ 0.04 0.04 0.04 0.040.04 0.03 0.03 R₂O/Al₂O₃ 1.05 1.04 1.02 0.99 0.98 1.14 0.96 Li₂O/Na₂O0.60 0.68 0.87 1.10 1.42 0.44 0.41 (R₂O + RO) − 0.14 −0.94 −1.68 −2.54−2.70 2.78 −1.16 Al₂O₃ − P₂O₅ Composition (mol %) Ex. 57 Ex. 58 Ex. 59Ex. 60 Ex. 61 Ex. 62 Ex. 63 Ex. 64 SiO₂ 58.32 63.3 63.3 63.3 63.3 63.363.3 63.46 Al₂O₃ 18.95 15.25 15.65 16.2 15.1 15.425 15.7 15.71 P₂O₅ 2.422.5 2.5 2.5 2.5 2.5 2.5 2.45 Li₂O 4.96 6 7 7.5 6 7 7.5 6.37 Na₂O 13.7410.7 9.7 9.45 10.55 9.475 8.95 10.69 ZnO 1.56 1.2 0.8 0 2.5 2.25 2 1.15MgO 0.02 1 1 1 0 0 0 0.06 SnO₂ 0.03 0.05 0.05 0.05 0.05 0.05 0.05 0.04R₂O/Al₂O₃ 0.99 1.10 1.07 1.05 1.10 1.07 1.05 1.09 Li₂O/Na₂O 0.36 0.560.72 0.79 0.57 0.74 0.84 0.6 (R₂O + RO) − −1.09 1.15 0.35 −0.75 1.450.80 0.25 −1.1 Al₂O₃ − P₂O₅

TABLE 1B Selected physical properties of the glasses listed in Table 1B.Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Density (g/cm³) 2.434 2.4932.434 2.504 2.44 2.514 2.519 Low temperature 8.9 8.62 8.95 8.6 8.82 8.718.54 CTE 25-300° C. (ppm/° C.) High temperature 17.67 19.1 17.16 2118.12 20 20.11 CTE (ppm/° C.) Strain pt. (° C.) 630 591 612 580 605 580589 Anneal pt. (° C.) 683 641 662 628 651 629 639 10¹¹ Poise 770 725 748710 734 711 721 temperature (° C.) Softening pt. (° C.) 937 888 919 873909 868 874 T^(35 kP) (° C.) 1167 1180 1158 1160 T^(200 kP) (° C.) 10701083 1061 1064 Zircon 1205 1220 1170 1185 1205 breakdown temperature (°C.) Zircon 1.56 × 10⁴ 4.15 × 10⁴ 2.29 × 10⁴ 1.74 × 10⁴ breakdownviscosity (P) Liquidus 980 990 975 990 1000 temperature (° C.) Liquidus1.15 × 10⁶ 2.17 × 10⁶ 9.39 × 10⁵ 7.92 × 10⁵ viscosity (P) Poisson'sratio 0.200 0.211 0.206 0.214 0.204 0.209 0.211 Young's 69.2 68.8 69.468.5 69.6 68.3 69.0 modulus (GPa) Refractive 1.4976 1.5025 1.4981 1.50291.4992 1.5052 1.506 index at 589.3 nm Stress optical 2.963 3.158 3.0133.198 2.97 3.185 3.234 coefficient (nm/mm/MPa) Ex. 8 Ex. 9 Ex. 10 Ex. 11Ex. 12 Ex. 13 Ex. 14 Density (g/cm³) 2.516 2.501 2.498 2.493 2.493 2.4922.486 Low temperature 8.35 8.67 8.87 8.49 8.65 8.71 8.49 CTE 25-300° C.(ppm/° C.) High temperature 20.11 20.6 20.94 19.52 20.77 CTE (ppm/° C.)Strain pt. (° C.) 590 589 591 584 600 579 588 Anneal pt. (° C.) 641 639640 628 652 620 630 10¹¹ Poise 726 724 720 704 738 695 704 temperature(° C.) Softening pt. (° C.) 888 890 865 857 900 867 860 T^(35 kP) (° C.)1170 1176 1159 1139 1197 1169 T^(200 kP) (° C.) 1073 1080 1061 1041 10991070 Zircon 1195 1195 1210 1225 1195 1195 1220 breakdown temperature (°C.) Zircon 2.33 × 10⁴ 2.58 × 10⁴ 1.60 × 10⁴ 9.94 × 10³ 3.63 × 10⁴ 2.35 ×10⁴ breakdown viscosity (P) Liquidus 1005 990 990 980 990 980 980temperature (° C.) Liquidus 8.69 × 10⁴ 1.48E+06 9.02E+05 7.10E+052.19E+06 1.33E+06 viscosity (P) Poisson's ratio 0.211 0.205 0.208 0.2090.209 0.210 0.217 Young's 69.0 68.7 71.4 73.5 68.4 71.6 74.0 modulus(GPa) Refractive 1.506 1.5036 1.505 1.5063 1.5026 1.5041 1.5052 index at589.3 nm Stress optical 3.234 3.194 3.157 3.131 3.18 3.156 3.131coefficient (nm/mm/MPa) Ex. 15 Ex. 16 Ex. 17 Ex. 18 Ex. 19 Ex. 20 Ex. 21Density (g/cm³) 2.433 2.429 2.426 2.431 2.428 2.433 2.486 Lowtemperature 9.15 9.16 8.83 8.97 8.97 8.79 8.45 CTE 25-300° C. (ppm/° C.)High temperature 20 20 21 17.3 20 CTE (ppm/° C.) Strain pt. (° C.) 615606 599 633 616 611 602 Anneal pt. (° C.) 662 659 653 684 670 665 65310¹¹ Poise 747 745 741 771 758 751 739 temperature (° C.) Softening pt.(° C.) 935 903 901 943 918 905 910 T^(35 kP) (° C.) 1182 1166 1152 12211185 1167 1207 T^(200 kP) (° C.) 1083 1066 1051 1122 1084 1066 1108Zircon breakdown temperature (° C.) Zircon breakdown viscosity (P)Liquidus temperature (° C.) Liquidus viscosity (P) Poisson's ratio 0.2030.207 0.205 0.209 0.199 0.207 Young's 68.9 71.2 72.7 69.4 70.9 68.1modulus (GPa) Refractive 1.4964 1.4981 1.4991 1.4965 1.4984 1.50061.5019 index at 589.3 nm Stress optical 2.994 3.022 2.982 2.979 2.99 03.173 coefficient (nm/mm/MPa) Ex. 22 Ex. 23 Ex. 24 Ex. 25 Ex. 26 Ex. 27Ex. 28 Density (g/cm³) 2.468 2.448 2.434 2.428 2.47 2.419 2.414 Lowtemperature 8.6 8.23 8.91 8.25 8.66 8.52 8.17 CTE 25-300° C. (ppm/° C.)High temperature 19.52 19.49 19.47 CTE (ppm/° C.) Strain pt. (° C.) 596595 638 616 608 640 620 Anneal pt. (° C.) 644 649 695 656 654 700 67710¹¹ Poise 728 741 785 732 736 798 771 temperature (° C.) Softening pt.(° C.) 905 922 941 925 911 978 946 T^(35 kP) (° C.) 1217 1227 1209 12151209 1283 1249 T^(200 kP) (° C.) 1115 1125 1109 1115 1107 1184 1150Zircon 1185 1185 1180 1185 1185 breakdown temperature (° C.) Zircon5.86E+04 6.91E+04 5.59E+04 5.72E+04 1.05E+05 breakdown viscosity (P)Liquidus 975 980 1080 1025 940 temperature (° C.) Liquidus 4.14E+064.52E+06 3.56E+05 1.27E+06 2.92E+07 viscosity (P) Poisson's ratio 0.2100.204 0.210 0.212 0.213 Young's 71.4 71.6 73.5 68.8 76.9 modulus (GPa)Refractive 1.502 1.5025 1.4996 1.5008 1.5006 1.4987 1.5014 index at589.3 nm Stress optical 3.123 3.03 3.001 3.021 3.148 3.039 3.015coefficient (nm/mm/MPa) Ex. 29 Ex. 30 Ex. 31 Ex. 32 Ex. 33 Ex. 34 Ex. 35Density 2.408 2.446 2.448 2.446 2.445 2.443 2.442 (g/cm³) Lowtemperature 7.86 8.29 8.38 8.17 8.14 8.04 7.97 CTE 25-300° C. (ppm/° C.)High temperature 18.57 19.71 CTE (ppm/° C.) Strain pt. (° C.) 610 591595 585 580 574 577 Anneal pt. (° C.) 665 645 649 638 633 627 629 10¹¹Poise 755 736 740 726 722 717 717 temperature (° C.) Softening pt. (°C.) 924 915 919 894 894 895 890 T^(35 kP) (° C.) 1216 1223 1227 12161210 1203 1196 T^(200 kP) (° C.) 1120 1122 1126 1114 1108 1102 1095Zircon 1210 1175 1180 1190 1195 1210 1205 breakdown temperature (° C.)Zircon 3.86E+04 7.72E+04 7.55E+04 5.29E+04 4.43E+04 3.14E+04 3.04E+04breakdown viscosity (P) Liquidus 1080 990 975 975 975 975 980temperature (° C.) Liquidus 4.55E+05 3.28E+06 5.43E+06 3.80E+06 3.33E+063.02E+06 2.29E+06 viscosity (P) Poisson's ratio 0.211 0.206 0.202 0.210.204 0.204 0.203 Young's 75.0 73.91 73.02 74.60 74.67 75.15 75.43modulus (GPa) Refractive 1.5053 1.503 1.5025 1.5035 1.5041 1.5046 1.5053index at 589.3 nm Stress optical 3.002 3.074 3.083 3.071 3.059 3.0163.053 coefficient (nm/mm/MPa) Ex. 29 Ex. 30 Ex. 31 Ex. 32 Ex. 33 Ex. 34Ex. 35 Density (g/cm³) 2.408 2.446 2.448 2.446 2.445 2.443 2.442 Lowtemperature 7.86 8.29 8.38 8.17 8.14 8.04 7.97 CTE 25-300° C. (ppm/° C.)High temperature 18.57 19.71 CTE (ppm/° C.) Strain pt. (° C.) 610 591595 585 580 574 577 Anneal pt. (° C.) 665 645 649 638 633 627 629 10¹¹Poise 755 736 740 726 722 717 717 temperature (° C.) Softening pt. (°C.) 924 915 919 894 894 895 890 T^(35 kP) (° C.) 1216 1223 1227 12161210 1203 1196 T^(200 kP) (° C.) 1120 1122 1126 1114 1108 1102 1095Zircon 1210 1175 1180 1190 1195 1210 1205 breakdown temperature (° C.)Zircon 3.86E+04 7.72E+04 7.55E+04 5.29E+04 4.43E+04 3.14E+04 3.04E+04breakdown viscosity (P) Liquidus 1080 990 975 975 975 975 980temperature (° C.) Liquidus 4.55E+05 3.28E+06 5.43E+06 3.80E+06 3.33E+063.02E+06 2.29E+06 viscosity (P) Poisson's ratio 0.211 0.206 0.202 0.210.204 0.204 0.203 Young's 75.0 73.91 73.02 74.60 74.67 75.15 75.43modulus (GPa) Refractive 1.5053 1.503 1.5025 1.5035 1.5041 1.5046 1.5053index at 589.3 nm Stress optical 3.002 3.074 3.083 3.071 3.059 3.0163.053 coefficient (nm/mm/MPa) Ex. 36 Ex. 37 Ex. 38 Ex. 39 Ex. 40 Ex. 41Ex. 42 Density (g/cm³) 2.453 2.453 2.452 2.451 2.449 2.449 2.425 Lowtemperature 8.17 8.14 7.97 8.01 7.79 7.9 8.54 CTE 25-300° C. (ppm/° C.)High temperature 20.56 CTE (ppm/° C.) Strain pt. (° C.) 595 595 584 587578 584 617 Anneal pt. (° C.) 649 649 638 640 630 637 663 10¹¹ Poise 740741 729 730 718 726 746 temperature (° C.) Softening pt. (° C.) 918 921905 907 894 901 929 T^(35 kP) (° C.) 1229 1232 1212 1219 1200 1204 1232T^(200 kP) (° C.) 1128 1131 1111 1118 1100 1103 1132 Zircon 1185 12001210 breakdown temperature (° C.) Zircon 7.20E+04 4.26E+04 3.00E+04breakdown viscosity (P) Liquidus 995 990 965 temperature (° C.) Liquidus3.33E+06 2.51E+06 3.71E+06 viscosity (P) Poisson's ratio 0.208 0.2060.206 Young's 73.70 74.67 75.50 modulus (GPa) Refractive 1.5032 1.50421.5054 1.5005 index at 589.3 nm Stress optical 3.093 3.071 3.072 3.033coefficient (nm/mm/MPa) Ex. 43 Ex. 44 Ex. 45 Ex. 46 Ex. 47 Ex. 48 Ex. 49Ex. 50 Density (g/cm³) 2.424 2.422 2.455 2.454 2.454 2.434 2.439 2.443Low temperature 8.48 8.34 8.03 7.88 7.76 7.87 7.71 7.63 coefficient ofthermal expansion 25-300° C. (ppm/° C.) High temperature coefficient ofthermal expansion (ppm/° C.) Strain pt. 614 594 595 586 579 580 581 579temperature (° C.) Anneal pt. 659 640 649 639 630 633 633 632temperature (° C.) 10¹¹ Poise 739 722 740 729 718 722 721 721temperature (° C.) Softening pt. 912 899 918 909 898 892 893 895temperature (° C.) 35 kP 1216 1204 1212 1200 1203 1203 1203 temperature(° C.) 200 kP 1116 1102 1113 1099 1105 1102 1103 temperature (° C.)Zircon breakdown temperature (° C.) Zircon breakdown viscosity (P)Liquidus 985 965 1005 1010 1030 temperature (° C.) Liquidus 4.E+061.78E+06 1.34E+06 8.98E+05 viscosity (P) Poisson's ratio 0.211 0.210.213 Young's 76.32 76.60 76.81 modulus (GPa) Refractive 1.5014 1.50261.5036 1.5047 1.5061 1.505 1.5059 1.5064 index at 589.3 nm Stressoptical 2.965 2.981 3.082 3.057 3.063 3.025 3.004 3.046 coefficient(nm/mm/MPa) Ex. 51 Ex. 52 Ex. 53 Ex. 54 Ex. 55 Ex. 56 Ex. 57 Density(g/cm³) 2.424 2.431 2.403 2.4 2.45 2.462 2.468 Low temperature 77.1 76.174.3 73.1 80.2 79.7 83.6 CTE 25-300° C. (ppm/° C.) High temperature CTE(ppm/° C.) Strain pt. (° C.) 588 599 611 612 580 611 597 Anneal pt. (°C.) 640 651 665 665 631 663 649 10¹¹ Poise 728 738 753 752 718 750 735temperature (° C.) Softening pt. (° C.) 900.4 907.5 916 912.5 892.2915.6 899.4 T^(35 kP) (° C.) 1204 1209 1209 1202 1206 1205 1184T^(200 kP) (° C.) 1106 1113 1113 1106 1102 1111 1093 Zircon breakdowntemperature (° C.) Zircon breakdown viscosity (P) Liquidus 1060 11151160 1205 temperature (° C.) Liquidus 5.11E+05 1.90E+05 8.18E+043.32E+04 viscosity (P) Poisson's ratio 0.211 0.212 0.208 0.214 Young's77.01 78.05 77.57 78.74 modulus (GPa) Refractive 1.5054 1.5055 1.50591.5072 index at 589.3 nm Stress optical 3.011 2.98 2.982 2.964coefficient (nm/mm/MPa) Ex. 64 Density (g/cm³) 2.428 CTE 25-300° C. 7.8(ppm/° C.) Strain pt. (° C.) 571 Anneal pt. (° C.) 622 10¹¹ Poisetemperature (° C.) Softening pt. (° C.) 881.4 T^(35 kP) (° C.)T^(200 kP) (° C.) 1645 Zircon breakdown temperature (° C.) Zirconbreakdown viscosity (P) Liquidus 1000 temperature (° C.) Liquidus1524280 viscosity (P) Poisson's ratio 0.211 Young's 76.3 modulus (GPa)Refractive 1.51 index at 589.3 nm Stress optical 3.02 coefficient(nm/mm/MPa)

Where the glass article includes a glass-ceramic, the crystal phases mayinclude β-spodumene, rutile, gahnite or other known crystal phases andcombinations thereof.

The glass article may be substantially planar, although otherembodiments may utilize a curved or otherwise shaped or sculptedsubstrate. In some instances, the glass article may have a 3D or 2.5Dshape. The glass article may be substantially optically clear,transparent and free from light scattering. The glass article may have arefractive index in the range from about 1.45 to about 1.55. As usedherein, the refractive index values are with respect to a wavelength of550 nm.

Additionally or alternatively, the thickness of the glass article may beconstant along one or more dimension or may vary along one or more ofits dimensions for aesthetic and/or functional reasons. For example, theedges of the glass article may be thicker as compared to more centralregions of the glass article. The length, width and thickness dimensionsof the glass article may also vary according to the article applicationor use.

The glass article may be characterized by the manner in which it isformed. For instance, where the glass article may be characterized asfloat-formable (i.e., formed by a float process), down-drawable and, inparticular, fusion-formable or slot-drawable (i.e., formed by a downdraw process such as a fusion draw process or a slot draw process).

A float-formable glass article may be characterized by smooth surfacesand uniform thickness is made by floating molten glass on a bed ofmolten metal, typically tin. In an example process, molten glass that isfed onto the surface of the molten tin bed forms a floating glassribbon. As the glass ribbon flows along the tin bath, the temperature isgradually decreased until the glass ribbon solidifies into a solid glassarticle that can be lifted from the tin onto rollers. Once off the bath,the glass article can be cooled further and annealed to reduce internalstress. Where the glass article is a glass ceramic, the glass articleformed from the float process may be subjected to a ceramming process bywhich one or more crystalline phases are generated.

Down-draw processes produce glass articles having a uniform thicknessthat possess relatively pristine surfaces. Because the average flexuralstrength of the glass article is controlled by the amount and size ofsurface flaws, a pristine surface that has had minimal contact has ahigher initial strength. When this high strength glass article is thenfurther strengthened (e.g., chemically), the resultant strength can behigher than that of a glass article with a surface that has been lappedand polished. Down-drawn glass articles may be drawn to a thickness ofless than about 2 mm. In addition, down drawn glass articles have a veryflat, smooth surface that can be used in its final application withoutcostly grinding and polishing. Where the glass article is a glassceramic, the glass article formed from the down draw process may besubjected to a ceramming process by which one or more crystalline phasesare generated.

The fusion draw process, for example, uses a drawing tank that has achannel for accepting molten glass raw material. The channel has weirsthat are open at the top along the length of the channel on both sidesof the channel. When the channel fills with molten material, the moltenglass overflows the weirs. Due to gravity, the molten glass flows downthe outside surfaces of the drawing tank as two flowing glass films.These outside surfaces of the drawing tank extend down and inwardly sothat they join at an edge below the drawing tank. The two flowing glassfilms join at this edge to fuse and form a single flowing glass article.The fusion draw method offers the advantage that, because the two glassfilms flowing over the channel fuse together, neither of the outsidesurfaces of the resulting glass article comes in contact with any partof the apparatus. Thus, the surface properties of the fusion drawn glassarticle are not affected by such contact. Where the glass article is aglass ceramic, the glass article formed from the fusion process may besubjected to a ceramming process by which one or more crystalline phasesare generated.

The slot draw process is distinct from the fusion draw method. In slowdraw processes, the molten raw material glass is provided to a drawingtank. The bottom of the drawing tank has an open slot with a nozzle thatextends the length of the slot. The molten glass flows through theslot/nozzle and is drawn downward as a continuous glass article and intoan annealing region. Where the glass article is a glass ceramic, theglass article formed from the slot draw process may be subjected to aceramming process by which one or more crystalline phases are generated.

In some embodiments, the glass article may be formed using a thinrolling process, as described in U.S. Pat. No. 8,713,972, entitled“Precision Glass Roll Forming Process and Apparatus”, U.S. Pat. No.9,003,835, entitled “Precision Roll Forming of Textured Sheet Glass”,U.S. Patent Publication No. 20150027169, entitled “Methods And ApparatusFor Forming A Glass Ribbon”, and U.S. Patent Publication No.20050099618, entitled “Apparatus and Method for Forming Thin GlassArticles”, the contents of which are incorporated herein by reference intheir entirety. More specifically the glass article may be formed bysupplying a vertical stream of molten glass, forming the supplied streamof molten glass or glass-ceramic with a pair of forming rolls maintainedat a surface temperature of about 5000° C. or higher or about 600° C. orhigher to form a formed glass ribbon having a formed thickness, sizingthe formed ribbon of glass with a pair of sizing rolls maintained at asurface temperature of about 400° C. or lower to produce a sized glassribbon having a desired thickness less than the formed thickness and adesired thickness uniformity. The apparatus used to form the glassribbon may include a glass feed device for supplying a supplied streamof molten glass; a pair of forming rolls maintained at a surfacetemperature of about 500° C. or higher, the forming rolls being spacedclosely adjacent each other defining a glass forming gap between theforming rolls with the glass forming gap located vertically below theglass feed device for receiving the supplied stream of molten glass andthinning the supplied stream of molten glass between the forming rollsto form a formed glass ribbon having a formed thickness; and a pair ofsizing rolls maintained at a surface temperature of about 4000° C. orlower, the sizing rolls being spaced closely adjacent each otherdefining a glass sizing gap between the sizing rolls with the glasssizing gap located vertically below the forming rolls for receiving theformed glass ribbon and thinning the formed glass ribbon to produce asized glass ribbon having a desired thickness and a desired thicknessuniformity.

In some instances, the thin rolling process may be utilized where theviscosity of the glass does not permit use of fusion or slot drawmethods. For example, thin rolling can be utilized to form the glassarticles when the glass exhibits a liquidus viscosity less than 100 kP.

The glass article may be acid polished or otherwise treated to remove orreduce the effect of surface flaws.

Another aspect of this disclosure pertains to a method of forming afracture-resistant glass article. The method includes providing a glasssubstrate having a first surface and a second surface defining athickness of about 1 millimeter or less and generating a stress profilein the glass substrate, as described herein to provide thefracture-resistant glass article. In one or more embodiments, generatingthe stress profile comprises ion exchanging a plurality of alkali ionsinto the glass substrate to form an alkali metal oxide concentrationgradient comprising a non-zero concentration of alkali metal oxideextending along the thickness. In one example, generating the stressprofile includes immersing the glass substrate in a molten salt bathincluding nitrates of Na+, K+, Rb+, Cs+ or a combination thereof, havinga temperature of about 350° C. or greater (e.g., about 350° C. to about500° C.). In one example, the molten bath may include NaNO₃ and may havea temperature of about 485° C. In another example, the bath may includeNaNO₃ and have a temperature of about 430° C. The glass substrate may beimmersed in the bath for about 2 hours or more, up to about 48 hours(e.g., from about 12 hours to about 48 hours, from about 12 hours toabout 32 hours, from about 16 hours to about 32 hours, from about 16hours to about 24 hours, or from about 24 hours to about 32 hours).

In some embodiments, the method may include chemically strengthening orion exchanging the glass substrate in more than one step usingsuccessive immersion steps in more than one bath. For example, two ormore baths may be used successively. The composition of the one or morebaths may include a single metal (e.g., Ag+, Na+, K+, Rb+, or Cs+) or acombination of metals in the same bath. When more than one bath isutilized, the baths may have the same or different composition and/ortemperature as one another. The immersion times in each such bath may bethe same or may vary to provide the desired stress profile.

In one or more embodiments, a second bath or subsequent baths may beutilized to generate a greater surface CS. In some instances, the methodincludes immersing the glass material in the second or subsequent bathsto generate a greater surface CS, without significantly influencing thechemical depth of layer and/or the DOC. In such embodiments, the secondor subsequent bath may include a single metal (e.g., KNO₃ or NaNO₃) or amixture of metals (KNO₃ and NaNO₃). The temperature of the second orsubsequent bath may be tailored to generate the greater surface CS. Insome embodiments, the immersion time of the glass material in the secondor subsequent bath may also be tailored to generate a greater surface CSwithout influencing the chemical depth of layer and/or the DOC. Forexample, the immersion time in the second or subsequent baths may beless than 10 hours (e.g., about 8 hours or less, about 5 hours or less,about 4 hours or less, about 2 hours or less, about 1 hour or less,about 30 minutes or less, about 15 minutes or less, or about 10 minutesor less).

In one or more alternative embodiments, the method may include one ormore heat treatment steps which may be used in combination with theion-exchanging processes described herein. The heat treatment includesheat treating the glass article to obtain a desired stress profile. Insome embodiments, heat treating includes annealing, tempering or heatingthe glass material to a temperature in the range from about 300° C. toabout 600° C. The heat treatment may last for 1 minute up to about 18hours. In some embodiments, the heat treatment may be used after one ormore ion-exchanging processes, or between ion-exchanging processes.

EXAMPLES

Various embodiments will be further clarified by the following examples.

Example 1

Glass articles according to Examples 1A-1B and Comparative Examples1C-1G were made by providing glass substrates having a nominal glasscomposition of 58 mol % SiO₂, 16.5 mol % Al₂O₃, 17 mol % Na₂O, 3 mol %MgO, and 6.5 mol % P₂O₅. The glass substrates had a thickness of 0.4 mmand length and width dimensions of 50 mm. The glass substrates werechemically strengthened by an ion exchange process that includedimmersing in a molten salt bath of 80% KNO3 and 20% NaNO₃ having atemperature of about 420° C. for the durations shown in Table 2. Theresulting glass articles were then subjected to AROR testing asdescribed above and by abrading a major surface of each of the samplesusing 90 grit SiC particles at a pressure of 5 psi, 15 psi or 25 psi, asalso shown in Table 2. Table 2 shows the average equibiaxial flexuralstrength or failure load of the glass articles.

TABLE 2 Chemical strengthening conditions and AROR results forExample 1. At 5 psi 15 psi 25 psi Ion Exchange Average kgf Average kgfAverage kgf Ex. Conditions (stdev) (stdev) (stdev) 1C 420° C./4 hours49.4 (7.1) 17.4 (7.2) 0.3 (0.9) 1D 420° C./8 hours 49.9 (7.1) 36.5 (6.7)19.3 (6.4) 1A 420° C./16 hours 47.5 (6.0) 38.3 (2.8) 30.0 (5.4) 1B 420°C./32 hours 36.9 (4.3) 30.9 (3.1) 26.2 (2.8) 1E 420° C./64 hours 18.7(1.5) 15.3 (0.9) 13.5 (1.2) 1F 420° C./128 hours 5.9 (0.5) 5.4 (0.3) 4.5(0.3)

The average equibiaxial flexural strength or failure load of theExamples after abrasion at 15 psi and 25 psi are plotted in FIG. 11 . Asshown in FIG. 11 , Examples 1A and 1B exhibited the greatest averageequibiaxial flexural strength after being abraded at 25 psi.Accordingly, the AROR performance of Examples 1A and 1B demonstrate thatthese glass articles exhibit a highly diced fracture pattern, whichindicates improved retained strength, especially for deeper abrasiondepths that result from higher abrasion pressures.

Example 2

Glass articles according to Examples 2A-2C and Comparative Examples2D-2F were made by providing glass substrates and chemicallystrengthening the glass substrates. The glass substrates used forExamples 2A-2C and Comparative 2E-2F had a nominal glass composition of69.2 mol % SiO₂, 12.6 mol % Al₂O₃, 1.8 mol % B₂O₃, 7.7 mol % Li₂O, 0.4mol % Na₂O, 2.9 mol % MgO, 1.7 mol % ZnO, 3.5 mol % TiO₂ and 0.1 mol %SnO₂. The substrate used for Comparative Example 2D had the samecomposition as Example 1.

The glass substrates had a thickness of 1 mm and length and widthdimensions permitting assembly with a known mobile device housing. Theglass substrates were chemically strengthened by the ion exchangeprocesses shown in Table 3. The CT and DOC values for Examples 2A-2Cwere measured by SCALP and are also shown in Table 3.

TABLE 3 Ion exchange conditions and drop testing results for Example 2Molten Bath Molten Bath Temperature Time CT DOC Example Composition (°C.) (hours) (MPa) (μm) Ex. 2A 100% 430 24 128 160 NaNO3 Ex. 2B 100% 43029 153 200 NaNO3 Ex. 2C 100% 430 33 139 200 NaNO3 Comp. Ex. 2D Comp. Ex.100% 390 3.5 2E NaNO3 Comp. Ex. 100% 430 48 2F NaNO3

Comparative Example 2D was ion exchanged to exhibit an error functionstress profile with a DOC exceeding 75 micrometers (as measured byRoussev I applying IWKB analysis). The resulting glass articles werethen retrofitted to identical mobile device housings and subjected todrop testing as described above onto 30 grit sand paper. FIG. 12 showsthe maximum failure height for the Examples. As shown in FIG. 12 ,Examples 2A-2C exhibited significantly greater maximum failure heights(i.e., 212 cm, 220 cm, and 220 cm, respectively) and exhibited dicingbehavior. Example 2F, which has the same composition, did not exhibitthe same dicing behavior and exhibited a lower maximum failure height,as compared to Examples 2A-2C.

Example 3

Glass articles according to Examples 3A-3K and Comparative Examples3L-3X were made by providing glass substrates and strengthening theglass substrates. The substrates used for Examples 3A-3D had the samecomposition as Example 1 and the substrates used for Examples 3L-3X hada nominal glass composition of 69 mol % SiO₂, 10.3 mol % Al₂O₃, 15.2 mol% Na₂O, 5.4 mol % MgO, and 0.2 mol % SnO₂.

The glass substrates had a thickness of 0.4 mm and length and widthdimensions of 50 mm by 50 mm. The glass substrates were chemicallystrengthened by ion exchange. Examples 3A-3K were ion exchanged in amolten salt bath of 80% KNO₃ and 20% NaNO₃ having a temperature of 460°C. for 12 hours. Comparative Examples 3L-3X were ion exchanged such thateach resulting glass article exhibits a surface CS of 912 MPa and a DOCof 37 μm, as measured by FSM.

The resulting glass articles were then subjected to fracture byimpacting one major surface of each article with a tungsten carbideconospherical scribe for a single strike from a drop distance (asindicated in Tables 4 and 5) and assessing the breakage or fracturepattern in terms of how many fragments resulted, whether the glassarticle fractured immediately or did not fracture at all, and thefrangibility of the glass article.

TABLE 4 Failure characteristics and fracture mechanics of Examples 3A-3KFragment Drop Strike Count Frangible Distance Time to Ex. Count (#)(Y/N) (inches) fracture 3A 1 100+ Yes 0.611 Instant 3B 1 DNB DNB 0.561DNB 3C 1 DNB DNB 0.511 DNB 3D 1 DNB DNB 0.461 DNB 3E 1 DNB DNB 0.411 DNB3F 1 DNB DNB 0.361 DNB 3G 1 DNB DNB 0.311 DNB 3H 1 100+ Yes 0.261Instant 3I 1 DNB DNB 0.211 DNB 3J 1 DNB DNB 0.161 DNB 3K 1 DNB DNB 0.111DNB *DNB = did not break

TABLE 5 Failure characteristics and fracture mechanics of ComparativeExamples 3L-3X. Fragment Drop Strike Count Frangible Distance Time toEx. Count (#) (Y/N) (inches) fracture 3L 1 9 No 0.226 Instant 3M 1 7 No0.221 Instant 3N 1 5 Yes 0.216 30 seconds 3O 1 6 Yes 0.211 30 seconds 3P1 2 No 0.206 30 seconds 3Q 1 7 Yes 0.201  1 minute 3R 1 DNB DNB 0.196DNB 3S 1 5 Yes 0.191 30 seconds 3T 1 6 Yes 0.186 10 seconds 3U 1 9 Yes0.181 10 seconds 3V 1 6 Yes 0.176 15 seconds 3W 1 10+ Yes 0.171 10seconds 3X 1 8 Yes 0.111 30 seconds *DNB = did not break

As shown in Tables 4-5, it is clear that glass articles chemicallystrengthened to a condition near the frangibility limit (i.e.,Comparative Examples 3L-3X) are much more likely to experience a delayedfailure, when compared to glass articles that were chemicallystrengthened to a condition a high degree of dicing/fragmentation occursupon fracture (i.e., Examples 3A-3K). Specifically, more than 80% ofComparative Examples 3L-3X failed in a delayed manner, while the samplesin Table 4 either failed immediately, or did not break. Moreover,Comparative Examples 3L-3X exhibited fewer, larger, more splinteredfragments than Examples 3A-4K, which failed with a high degree of dicingand exhibited fragments with low aspect ratios.

Example 4

Glass articles according to Examples 4A-4B and Comparative Examples4C-4F were made by providing glass substrates having the same nominalcomposition as Example 1 and strengthening the glass substrates. Theglass substrates had a thickness of 0.4 mm and were chemicallystrengthened by an ion exchange process in which the glass substrateswere immersed in a molten salt bath of 80% KNO₃ and 20% NaNO₃ having atemperature of 430° C. for the durations shown in Table 6.

TABLE 6 Ion exchange durations for Example 5 Immersion Example time(hours) Example 4A 16 Example 4B 32 Comparative Ex. 4C 4 Comparative Ex.4D 8 Comparative Ex. 4E 64 Comparative Ex. 4F 128

The concentration of K₂O in the glass articles was measured usingGlow-Discharge Optical Emission Spectroscopy (GDOES). In FIG. 13 , themol % (expressed as K₂O) of the larger K+ ion that is replacing thesmaller Na+ in the glass substrate is represented on the vertical axis,and plotted as a function of ion-exchange depth. Examples 4A and 4Bexhibited a higher stored tensile energy (and central tension) than theother profiles, and maximize the DOC as well as the magnitude of thesurface compression.

FIG. 14 shows the stress profile, as measured by Roussev I applying IWKBanalysis, of Example 4G which was formed by providing the same substrateas Examples 4A and 4B but and immersing in a molten salt bath of 70%KNO₃ and 30% NaNO₃ having a temperature of 460° C. for 12 hours.

Example 5

Glass articles according to Examples 5A-5D (with Examples B and C beingcomparative) were made by providing glass substrates having the samenominal composition as Example 2A-2C and strengthening the glasssubstrates. The glass substrates were chemically strengthened by the ionexchange processes shown in Table 7.

TABLE 7 Ion exchange conditions for Example 5. Molten Bath ImmersionMolten Bath Temperature duration Example Composition (° C.) (hours) 5A 80% KNO₃/20% 460 12 NaNO₃ Comparative 5B  65% KNO₃/35% 460 12 NaNO₃Comparative 5C 100% NaNO₃ 430 4 5D 100% NaNO₃ 430 16

Example 5A and Comparative Example 5B were adhered to a transparentsubstrate using a pressure sensitive adhesive supplied by 3M under thetradename 468MP, applied in the same manner and identical thicknesses.Example 5A and Comparative Example 5B were fractured and the resultingfractured glass articles were evaluated. FIGS. 15A and 15B show fractureimages of Example 5A and Comparative Example 5B, respectively. As shownin FIG. 15A, Example 5A exhibited higher dicing behavior and resulted infragments having an aspect ratio of less than about 2. As shown in FIG.15B, Comparative Example 5B resulted in fragments having a higher aspectratio.

Comparative Example 5C and Example 5D were not constrained by anadhesive and were fractured. The resulting fractured glass articles wereevaluated. FIGS. 15C and 15D show fracture images of Comparative Example5C and Example 5D, respectively. As shown in FIG. 15C, ComparativeExample 5C exhibited larger fragments. As shown in FIG. 15D, Example 5Dresulted in fragments indicating dicing. It is believed that thesub-fragments (not shown) did not extend through the thickness of theglass article.

Example 6

A glass article according to Example 6 was made by providing a glasssubstrate having the same nominal composition as Examples 3A-3K andstrengthened in the same manner. Example 6 was evaluated for haze orreadability after fracture, at different viewing angles. After fracture,Example 6 exhibited a high degree of dicing but still exhibited goodreadability at a 90° viewing angle, relative to the surface plane ormajor surface of the glass article. The readability drops as the viewingangle decreases, as illustrated by the images of FIGS. 16A-16D. FIG. 16Ademonstrates text placed behind Example 6 is still visible and readableat a viewing angle of 90 degrees relative to the surface plane or majorsurface of the glass article. FIG. 16B shows the test is somewhatvisible and readable at a viewing angle of about 67.5 degrees. The textis not clear or readable at viewing angles of 45 degrees and 22.5degrees relative to the surface plane or major surface of the glassarticle, according to FIGS. 16C-16D. Accordingly, Example 6 can functionas a privacy screen when used in a display such that only the viewer mayread or see the display clearly, while others beside the viewer wouldnot be able to read the display clearly.

Example 7

Glass articles according to Examples 7A-7C were made by providing glasssubstrates having a 2.5-dimensional shape but each having a differentthickness (i.e., Example 7A had a thickness of 1 mm, Example 7B had athickness of 0.8 mm and Example 7C had a thickness of 0.5 mm). A2.5-dimensional shape includes a flat major surface and an oppositecurved major surface. The composition of the glass substrates was thesame as Examples 2A-2C. The stored tensile energy of each substrate wascalculated as a function of ion exchange time using a molten bath havinga temperature of 430° C. Stored tensile energy was calculated using thetotal amount of stress over the CT region (327 in FIG. 4 ) measured bySCALP. The calculated stored tensile energy was plotted as a function ofion exchange time in FIG. 17 . For purposes of illustration, a dottedline at a stored tensile energy value of 10 J/m² has been drawn torepresent an approximate threshold for frangibility. The highlightedarea represents the ion-exchange conditions for a single part having athickness range from 0.5-1.0 mm that exhibit the behaviors describedherein. Specifically, this range enables optimized mechanicalperformance and a similar degree of dicing across the area of the part,when and if the part fractures.

If known frangibility limits are used to determine the ion exchangeparameters for various thicknesses, at Time A the ion exchange timewhere the stored tensile energy reaches below 10 J/m², a glass substratehaving a thickness of 1 mm would be non-frangible, and a glass substratewith a thickness of 0.5 mm would have low CS. At time C, a glasssubstrate having a thickness of 0.5 mm is non-frangible, and a glasssubstrate having a thickness between 1 mm and 0.8 mm regions would beconsidered frangible. Accordingly, when using the current definition offrangibility, FIG. 17 shows that one would choose an ion-exchange timein a given bath at a designated temperature that is significantly longerfor a relatively thick part, or region of a non-uniformly thick part,than one would choose for a thinner part, or a thinner region, of anintentionally non-uniformly thick part. In order to provide afully-finished 2.5D part that has substantially improved dropperformance and reliability, and a relatively uniform degree offragmentation, or dicing, it may be desirable to ion-exchange the partfor a shorter period of time in order to install a higher degree ofstored tensile energy than would choose to limit the degree offragmentation or dicing.

FIG. 18 represents the samples shown in FIG. 17 , except that theinstalled tensile energy represented in 11 is now represented as centraltension (CT), which has been used as a more common descriptor of thetensile energy in the central region of the ion-exchanged specimens.

Example 8

Example 8 included a glass article made by providing a glass substratehaving the same nominal composition as Example 1 and strengthening theglass substrate. The glass substrate had a thickness of 0.4 mm and waschemically strengthened by a two-step ion exchange process in which theglass substrate was first immersed in a first molten salt bath of 80%KNO₃ and 20% NaNO₃ having a temperature of 460° C. for 12 hours, removedfrom the first molten salt bath and immersed in a second molten saltbath of 100% KNO₃ having a temperature of 390° C. for 12 minutes. Theresulting glass article had a surface compressive stress of 624.5 MPa, aDOC of about 83.3 micrometers (which is equivalent to 0.208t) and a maxCT of about 152.6 MPa, measured by Roussev I applying IWKB analysis.FIG. 19 shows the compressive stress (shown as negative values) andtensile stress (shown as positive values) as a function of depth inmicrometers.

Aspect (1) of this disclosure pertains to a strengthened glass articlecomprising: a first surface and a second surface opposing the firstsurface defining a thickness (t) of about 1.1 mm or less; a compressivestress layer extending from the first surface to a depth of compression(DOC) of greater than about 0.11·t; wherein, after the glass articlefractures according to a Frangibility Test, the glass article includes aplurality of fragments, wherein at least 90% of the plurality offragments have an aspect ratio of about 5 or less.

Aspect (2) of this disclosure pertains to the strengthened glass articleof Aspect (1), wherein the glass article fractures into the plurality offragments in 1 second or less, as measured by the Frangibility Test.

Aspect (3) of this disclosure pertains to the strengthened glass articleof Aspect (1) or Aspect (2), wherein at least 80% of the plurality offragments have a maximum dimension that is less than or equal to 3·t.

Aspect (4) of this disclosure pertains to the strengthened glass articleof any one of Aspects (1) through Aspect (3), wherein at least 50% ofplurality of fragments comprises an aspect ratio of 2 or less.

Aspect (5) of this disclosure pertains to the strengthened glass articleof any one of Aspects (1) through Aspect (4), wherein at least 50% ofthe plurality of fragments comprises a volume of less than or equal toabout 10 mm³.

Aspect (6) of this disclosure pertains to the strengthened glass articleof any one of Aspects (1) through Aspect (5), wherein the plurality offragments comprises an ejected portion of fragments, wherein the ejectedportion of fragments comprises 10% or less of the plurality offragments.

Aspect (7) of this disclosure pertains to the strengthened glass articleof any one of Aspects (1) through Aspect (6), wherein the glass articlecomprises a first weight prior to fracture and the wherein the pluralityof fragments comprises an ejected portion of fragments and a non-ejectedportion of fragments, the non-ejected portion of fragments having asecond weight, and the difference between the first weight and thesecond weight is 1% of the first weight.

Aspect (8) of this disclosure pertains to the strengthened glass articleof any one of Aspects (1) through Aspect (7), wherein the probability ofthe glass article fracturing into the plurality of fragments within 1second or less, as measured by a Frangibility Test, is 99% or greater.

Aspect (9) of this disclosure pertains to the strengthened glass articleof any one of Aspects (1) through Aspect (8), wherein the glass articlecomprises a stored tensile energy of 20 J/m² or greater.

Aspect (10) of this disclosure pertains to the strengthened glassarticle of any one of Aspects (1) through Aspect (9), wherein the glassarticle comprises a surface compressive stress and a central tension,wherein the ratio of central tension to surface compressive stress is inthe range from about 0.1 to about 1.

Aspect (11) of this disclosure pertains to the strengthened glassarticle of Aspect (10), wherein the central tension is 100 MPa/√(t/1 mm)or greater (in units of MPa), wherein t is in mm.

Aspect (12) of this disclosure pertains to the strengthened glassarticle of any one of Aspect (10) through Aspect (11), wherein thecentral tension is 50 MPa or greater.

Aspect (13) of this disclosure pertains to the strengthened glassarticle of any one of Aspect (10) through Aspect (12), wherein thesurface compressive stress is 150 MPa or greater.

Aspect (14) of this disclosure pertains to the strengthened glassarticle of any one of Aspect (10) through Aspect (13), wherein thesurface compressive stress is 400 MPa or greater.

Aspect (15) of this disclosure pertains to the strengthened glassarticle of any one of Aspect (10) through Aspect (14), wherein the DOCcomprises about 0.2t or greater.

Aspect (16) of this disclosure pertains to the strengthened glassarticle of any one of Aspect (1) through Aspect (15), wherein the glassarticle comprises an alkali aluminosilicate glass, alkali containingborosilicate glass, an alkali aluminophosphosilicate glass or alkalialuminoborosilicate glass.

Aspect (17) of this disclosure pertains to the strengthened glassarticle of any one of Aspect (1) through Aspect (16), wherein the glassarticle is disposed on a containment layer.

Aspect (18) of this disclosure pertains to a strengthened glass articlecomprising: a first surface and a second surface opposing the firstsurface defining a thickness (t) of about 1.1 mm or less; a compressivestress layer extending from the first surface to a depth of compression(DOC) of about greater than about 0.11·t, wherein the glass articleexhibits a load to failure of about 10 kgf or greater, after beingabraded with 90-grit SiC particles at a pressure of 25 psi for 5seconds.

Aspect (19) of this disclosure pertains to the strengthened glassarticle of Aspect (18), wherein the glass article comprises a storedtensile energy of 20 J/m² or greater.

Aspect (20) of this disclosure pertains to the strengthened glassarticle of any one of Aspect (18) or Aspect (19), The strengthened glassarticle of claim 18 or claim 19, wherein the glass article comprises asurface compressive stress and a central tension, wherein the ratio ofcentral tension to surface compressive stress is in the range from about0.1 to about 1.

Aspect (21) of this disclosure pertains to the strengthened glassarticle of Aspect (20), wherein the central tension (CT) is 50 MPa orgreater.

Aspect (22) of this disclosure pertains to the strengthened glassarticle of Aspect (20) or Aspect (21), wherein the surface compressivestress is 150 MPa or greater.

Aspect (23) of this disclosure pertains to the strengthened glassarticle of any one of Aspect (20) through Aspect (22), wherein thesurface compressive stress is 400 MPa or greater.

Aspect (24) of this disclosure pertains to the strengthened glassarticle of any one of Aspect (20) through Aspect (23), wherein the DOCcomprises about 0.2t or greater.

Aspect (25) of this disclosure pertains to the strengthened glassarticle of any one of Aspect (18) through Aspect (24), wherein the glassarticle comprises an alkali aluminosilicate glass, alkali containingborosilicate glass, alkali aluminophosphosilicate glass or alkalialuminoborosilicate glass.

Aspect (26) of this disclosure pertains to the strengthened glassarticle of any one of Aspect (20) through Aspect (25), wherein the glassarticle is adhered to a substrate.

Aspect (27) of this disclosure pertains to a device comprising: astrengthened glass substrate; a containment layer; and a support,wherein the strengthened glass substrate comprises a first surface and asecond surface opposing the first surface defining a thickness (t) ofabout 1.1 mm or less, a compressive stress layer extending from thefirst surface to a depth of compression (DOC) of greater than about 0.11t and, and a central tension (CT) of 50 MPa or greater, wherein thedevice comprises a tablet, a transparent display, a mobile phone, avideo player, an information terminal device, an e-reader, a laptopcomputer, or a non-transparent display.

Aspect (28) pertains to the device of Aspect (27), wherein, after theglass article fractures according to a Frangibility Test, the glassarticle includes a plurality of fragments having an aspect ratio ofabout 5 or less.

Aspect (29) pertains to the device of Aspect (27) or Aspect (28),wherein the glass article fractures into the plurality of fragments in 1second or less, as measured by the Frangibility Test.

Aspect (30) pertains to the device of Aspect (28) or Aspect (29),wherein at least 80% of the plurality of fragments have a maximumdimension that is less than or equal to 5·t.

Aspect (31) pertains to the device of any one of Aspects (28) throughAspect (30), wherein at least 50% of plurality of fragments eachcomprise an aspect ratio of 2 or less.

Aspect (32) pertains to the device of any one of Aspects (28) throughAspect (31), wherein at least 50% of the plurality of fragmentscomprises a volume of less than or equal to about 10 mm³.

Aspect (33) pertains to the device of any one of Aspects (28) throughAspect (32), wherein the plurality of fragments comprises an ejectedportion of fragments, wherein the ejected portion of fragments comprises10% or less of the plurality of fragments.

Aspect (34) pertains to the device of any one of Aspects (28) throughAspect (33), wherein the glass article comprises a first weight prior tofracture and the wherein the plurality of fragments comprises an ejectedportion of fragments and a non-ejected portion of fragments, thenon-ejected portion of fragments having a second weight, and thedifference between the first weight and the second weight is 1% of thefirst weight.

Aspect (35) pertains to the device of any one of Aspects (28) throughAspect (34), wherein the probability of the glass article fracturinginto the plurality of fragments within 1 second or less, as measured bythe Frangibility Test, is 99% or greater.

Aspect (36) pertains to the device of any one of Aspects (28) throughAspect (35), wherein the glass article comprises a stored tensile energyof 20 J/m² or greater.

Aspect (37) pertains to the device of any one of Aspects (27) throughAspect (36), wherein the glass article comprises a surface compressivestress and a central tension, wherein the ratio of central tension tosurface compressive stress is in the range from about 0.1 to about 1.

Aspect (38) pertains to the device of Aspect (37), wherein the surfacecompressive stress is 150 MPa or greater.

Aspect (39) pertains to the device of any one of Aspects (27) throughAspect (38), The device of any one of claims 27-38, wherein the DOCcomprises about 0.2t or greater.

Aspect (40) pertains to the device of any one of Aspects (27) throughAspect (39), wherein the glass article comprises an alkalialuminosilicate glass, alkali containing borosilicate glass, alkalialuminophosphosilicate glass or alkali aluminoborosilicate glass.

Aspect (41) pertains to the device of any one of Aspects (27) throughAspect (40), wherein the glass article is disposed on a containmentlayer.

Aspect (42) pertains to a strengthened glass article comprising: a firstsurface and a second surface opposing the first surface defining athickness (t) of about 1.1 mm or less; a compressive stress layerextending from the first surface to a depth of compression (DOC) ofgreater than about 0.11·t; wherein, after the glass article is laminatedto a containment layer and is fractured according to a FrangibilityTest, the glass article comprises fractures, and wherein at least 5% ofthe fractures extend only partially through the thickness.

Aspect (43) pertains to the strengthened glass article of Aspect (42),wherein the glass article fractures into the plurality of fragments in 1second or less, as measured by the Frangibility Test.

Aspect (44) pertains to the strengthened glass article of Aspect (42) orAspect (43), wherein the glass article comprises a stored tensile energyof 20 J/m² or greater.

Aspect (45) pertains to the strengthened glass article of any one ofAspect (42) through Aspect (44), wherein the glass article comprises asurface compressive stress and a central tension, wherein the ratio ofcentral tension to surface compressive stress is in the range from about0.1 to about 1.

Aspect (46) pertains to the strengthened glass article of Aspect (45),wherein the central tension is 50 MPa or greater.

Aspect (47) pertains to the strengthened glass article of Aspect (45) orAspect (46), wherein the surface compressive stress is 150 MPa orgreater.

Aspect (48) pertains to the strengthened glass article of any one ofAspect (42) through Aspect (47), wherein the DOC comprises about 0.2t orgreater.

Aspect (49) pertains to the strengthened glass article of any one ofAspect (42) through Aspect (48), wherein the glass article comprises analkali aluminosilicate glass, alkali containing borosilicate glass oralkali aluminoborosilicate glass.

Aspect (50) pertains to the strengthened glass article of any one ofAspect (42) through Aspect (49), wherein the glass article is disposedon a containment layer.

Aspect (51) pertains to a consumer electronic product comprising: ahousing having a front surface; electrical components provided at leastpartially internal to the housing, the electrical components includingat least a controller, a memory, and a display; and a cover glassdisposed at the front surface of the housing and over the display, thecover glass comprising a strengthened glass article, wherein thestrengthened glass article comprises: a first surface and a secondsurface opposing the first surface defining a thickness (t) of about 1.1mm or less; a compressive stress layer extending from the first surfaceto a depth of compression (DOC) of greater than about 0.11t; and acentral tension (CT) of about 50 MPa or greater.

Aspect (52) pertains to the consumer electronics device of Aspect (51),wherein, after the glass article fractures according to a FrangibilityTest, the glass article includes a plurality of fragments having anaspect ratio of about 5 or less, and

Aspect (53) pertains to the consumer electronics device of Aspect (52),wherein the glass article fractures into the plurality of fragments in 1second or less, as measured by the Frangibility Test.

Aspect (54) pertains to the consumer electronics device of Aspect (52)or Aspect (53), wherein at least 80% of the plurality of fragments havea maximum dimension that is less than or equal to 2·t.

Aspect (55) pertains to the consumer electronics device of any one ofAspect (52) through Aspect (54), wherein at least 50% of plurality offragments each comprise an aspect ratio of 2 or less.

Aspect (56) pertains to the consumer electronics device of any one ofAspect (52) through Aspect (55), wherein at least 50% of the pluralityof fragments comprises a volume of less than or equal to about 10 mm³.

Aspect (57) pertains to the consumer electronics device of any one ofAspect (52) through Aspect (56), wherein the plurality of fragmentscomprises an ejected portion of fragments, wherein the ejected portionof fragments comprises 10% or less of the plurality of fragments.

Aspect (58) pertains to the consumer electronics device of any one ofAspect (52) through Aspect (57), wherein the glass article comprises afirst weight prior to fracture and the wherein the plurality offragments comprises an ejected portion of fragments and a non-ejectedportion of fragments, the non-ejected portion of fragments having asecond weight, and the difference between the first weight and thesecond weight is 1% of the first weight.

Aspect (59) pertains to the consumer electronics device of any one ofAspect (53) through Aspect (58), wherein the probability of the glassarticle fracturing into the plurality of fragments within 1 second orless, as measured by the Frangibility Test, is 99% or greater.

Aspect (60) pertains to the consumer electronics device of any one ofAspect (51) through Aspect (59), wherein the glass article comprises astored tensile energy of 20 J/m² or greater.

Aspect (61) pertains to the consumer electronics device of any one ofAspect (51) through Aspect (60), wherein the glass article comprises asurface compressive stress and a central tension, wherein the ratio ofcentral tension to surface compressive stress is in the range from about0.1 to about 1.

Aspect (62) pertains to the consumer electronics device of Aspect (61),wherein the surface compressive stress is 150 or greater.

Aspect (63) pertains to the consumer electronics device of any one ofAspect (51) through Aspect (62), wherein the DOC comprises about 0.2t orgreater.

Aspect (64) pertains to the consumer electronics device of any one ofAspect (51) through Aspect (63), wherein the glass article comprises analkali aluminosilicate glass, alkali containing borosilicate glass,alkali aluminophosphosilicate or alkali aluminoborosilicate glass.

Aspect (65) pertains to the consumer electronics device of any one ofAspect (51) through Aspect (64), wherein the glass article is disposedon a containment layer.

Aspect (66) pertains to the consumer electronics device of any one ofAspect (51) through Aspect (65), wherein the consumer electronic productcomprises a tablet, a transparent display, a mobile phone, a videoplayer, an information terminal device, an e-reader, a laptop computer,or a non-transparent display.

Aspect (67) pertains to a package product comprising: a housingcomprising an opening, an exterior surface and an interior surfacedefining an enclosure; wherein the housing comprises a strengthenedglass article, wherein the strengthened glass article comprises: a firstsurface and a second surface opposing the first surface defining athickness (t) of about 1.1 mm or less; a compressive stress layerextending from the first surface to a depth of compression (DOC) ofgreater than about 0.11·t; and a central tension (CT) of 50 MPa orgreater.

Aspect (68) pertains to the package product of Aspect (67), wherein,after the glass article fractures according to a Frangibility Test, theglass article includes a plurality of fragments having an aspect ratioof about 5 or less, and wherein the glass article fractures into theplurality of fragments in 1 second or less, as measured by theFrangibility Test.

Aspect (69) pertains to the package product of Aspect (68), wherein atleast 80% of the plurality of fragments have a maximum dimension that isless than or equal to 2·t.

Aspect (70) pertains to the consumer electronics device of Aspect (68)or Aspect (69), wherein at least 50% of plurality of fragments eachcomprise an aspect ratio of 2 or less.

Aspect (71) pertains to the package product of any one of Aspect (68)through Aspect (70), wherein at least 50% of the plurality of fragmentscomprises a volume of less than or equal to about 10 mm³.

Aspect (72) pertains to the package product of any one of Aspect (68)through Aspect (71), wherein the plurality of fragments comprises anejected portion of fragments, wherein the ejected portion of fragmentscomprises 10% or less of the plurality of fragments.

Aspect (73) pertains to the package product of any one of Aspect (68)through Aspect (72), wherein the glass article comprises a first weightprior to fracture and the wherein the plurality of fragments comprisesan ejected portion of fragments and a non-ejected portion of fragments,the non-ejected portion of fragments having a second weight, and thedifference between the first weight and the second weight is 1% of thefirst weight.

Aspect (74) pertains to the package product of any one of Aspect (68)through Aspect (73), wherein the probability of the glass articlefracturing into the plurality of fragments within 1 second or less, asmeasured by the Frangibility Test, is 99% or greater.

Aspect (75) pertains to the package product of any one of Aspect (67)through Aspect (74), wherein the glass article comprises a storedtensile energy of 20 J/m² or greater.

Aspect (76) pertains to the package product of any one of Aspect (67)through Aspect (75), wherein the glass article comprises a surfacecompressive stress and a central tension, wherein the ratio of centraltension to surface compressive stress is in the range from about 0.1 toabout 1.

Aspect (77) pertains to the package product of Aspect (76), wherein thesurface compressive stress is 150 or greater.

Aspect (78) pertains to the package product of any one of Aspect (67)through Aspect (77), wherein the DOC comprises about 0.2t or greater.

Aspect (79) pertains to the package product of any one of Aspect (67)through Aspect (78), wherein the glass article comprises an alkalialuminosilicate glass, alkali containing borosilicate glass, alkalialuminophosphosilicate or alkali aluminoborosilicate glass.

Aspect (80) pertains to the package product of any one of Aspect (67)through Aspect (72), wherein the glass article is disposed on acontainment layer.

Aspect (81) pertains to the package product of any one of Aspect (67)through Aspect (80), further comprising a pharmaceutical material.

Aspect (82) pertains to the package product of any one of Aspect (67)through Aspect (81), further comprising a cap disposed in the opening.

It will be apparent to those skilled in the art that variousmodifications and variations can be made without departing from thespirit or scope of the invention.

What is claimed is:
 1. A method for producing a strengthened glass-basedarticle comprising: immersing a glass-based substrate having a thickness(t) of 3 mm or less into a first molten salt bath for about 2 hours toabout 48 hours, the first molten salt bath comprising a temperature fromabout 350° C. to 500° C. and sodium ions and potassium ions; immersingthe glass-based substrate into a second molten salt bath, after theimmersing into the first molten salt bath, for 10 hours or less, thesecond molten salt bath comprising a temperature of about 350° C. toabout 500° C. and potassium ions; whereby the immersing into the firstmolten salt bath and the immersing into the second molten salt bathresults in a strengthened glass-based article comprising a compressivestress layer extending from a first surface of the substrate to a depthof compression (DOC) of greater than 0.16·t, the compressive stresslayer comprising a surface compressive stress of 624.5 MPa or greater;and a maximum central tension that is 50 MPa or greater.
 2. The methodof claim 1, wherein: the DOC is as measured by scattered lightpolariscope; the compressive stress is as measured by a combination ofscattered light polariscope and surface stress meter; and the centraltension is as measured by scattered light polariscope.
 3. The method ofclaim 1, wherein the strengthened glass-based article comprises a storedtensile energy of 20 J/m² or greater.
 4. The method of claim 1, whereinthe ratio of the maximum central tension to the surface compressivestress is in the range from about 0.1 to about 1, and wherein themaximum central tension is 100 MPa/√(t/1 mm) or greater (in units ofMPa), wherein t is in mm.
 5. The method of claim 1, further comprisingdisposing the strengthened glass-based article on a containment layer.6. The method of claim 1, the strengthened glass-based article furthercomprising: a CT region of the stress profile, wherein the CT region isdefined by the equationStress(x)=MaxCT−(((MaxCT·(n+1))/0.5^(n))·|(x/t)−0.5|^(n)), wherein MaxCTis the maximum CT value and is provided as a positive value in units ofMPa, x is position along the thickness (t) in micrometers, and n isbetween 1.5 and 2.2.
 7. The method of claim 1, wherein, after thestrengthened glass-based article fractures according to a FrangibilityTest, the strengthened glass-based article includes a plurality offragments, wherein at least 90% of the plurality of fragments have anaspect ratio of about 5 or less.
 8. The method of claim 7, wherein thestrengthened glass-based article fractures into the plurality offragments in 1 second or less, as measured by the Frangibility Test. 9.The method of claim 7, wherein at least 80% of the plurality offragments have a maximum dimension that is less than or equal to 3·t.10. The method of claim 7, wherein at least 50% of plurality offragments comprises an aspect ratio of 2 or less.
 11. The method ofclaim 7, wherein at least 50% of the plurality of fragments comprises avolume of less than or equal to about 10 mm³.
 12. The method of claim 7,wherein the plurality of fragments comprises an ejected portion offragments, wherein the ejected portion of fragments comprises 10% orless of the plurality of fragments.
 13. The method of claim 7, whereinthe strengthened glass-based article comprises a first weight prior tofracture and wherein the plurality of fragments comprises an ejectedportion of fragments and a non-ejected portion of fragments, thenon-ejected portion of fragments having a second weight, and thedifference between the first weight and the second weight is 1% of thefirst weight.
 14. The method of claim 1, further comprising acompressive stress value at a maximum Potassium depth of layer that isin the range from about 50 MPa to about 300 MPa.
 15. The method of claim1, wherein the strengthened glass-based article exhibits a load tofailure of about 10 kgf or greater, after being abraded with 90-grit SiCparticles at a pressure of 25 psi for 5 seconds.
 16. The method of claim15, wherein the strengthened glass-based article comprises a storedtensile energy of 20 J/m² or greater.
 17. The method of claim 16,wherein the ratio of the maximum central tension to the surfacecompressive stress is in the range from about 0.1 to about 1, andwherein the maximum central tension (CT) is 85 MPa or greater.
 18. Themethod of claim 17, wherein the DOC comprises about 0.2t or greater. 19.The method of claim 18, wherein the strengthened glass-based article isadhered to a substrate.
 20. The method of claim 15, wherein t is 0.4 mmor more.